## MP Board Class 10th Science Solutions Chapter 16 Management of Natural Resources

### MP Board Class 10th Science Chapter 16 Intext Questions

Class 10th Science Chapter 16 Intext Questions Page No. 269

Question 1.
What changes can you make in your habits to become more environment friendly?

1.  We must refuse to buy products that harm us and the environment.
2.  We should minimise the use of electricity and water.
3.  We should encourage recycling of things.

Question 2.
What would be the advantages of exploiting resources with short-term aims?
With the human population increasing at a tremendous rate due to improvement in health-care, thedem and for all resources is increasing at an exponential rate. The management of natural resources requires a long term perspective so that these will last for the generations to come and will not merely be exploited to the hilt for short term gains.

Question 3.
How would these advantages differ from the advantages of using a long term perspective in managing our resources?
If resources are used in accordance with short term aims, present generation will be able to utilize the resources properly for overall development. But if we plan to use resources with long term aims, not only the present generation is benefited but also the future generations will also be able to utilize resources for fulfilling its necessities. Thus it would be better to use our natural resources with a long term perspective so that it could be used by the present generation as well as conserved for future use.

Question 4.
Why do you think that there should be equitable distribution of resources? What forces would be working against an equitable distribution of our resources?
Nature shows no partiality. Natural resources belong to all and these resources should be used judiciously. Equitable distribution of resources will benefit both poor as well as rich people.
Human greed, corruption, and the lobby of the rich and powerful are the forces working against an equitable distribution of our resources.

Class 10th Science Chapter 16 Intext Questions Page No. 273

Question 1.
Why should we conserve forests and wildlife?
We should conserve forests and wildlife to preserve the biodiversity (range of different life-forms) so as to avoid the loss of ecological stability. A large number of tribes are the habitants in and around the forests. If the forests are not conserved,- then it may affect these habitants. Without proper management of forest and wildlife, the quality of soil, the water sources and even the amount of rainfall may be affected. Without forest and wildlife, life would become impossible for human beings.

Question 2.
Suggest some approaches towards the conservation of forests.
Some approaches towards the conservation of forests are as follows:

(a) People should show their participation in saving the forest by protesting against the tv ting of trees. For example, Chipko Andolan.
(b) Planting of bees should be increased. Rate of afforestation must be more than that of deforestation.
(c) Some people cut precious trees such as sandalwood to earn money. Government should take legal steps to catch these wood smugglers.
(d) Habitants of forests must not be bothered by the forest officials. Otherwise, this would result in the clash between tribal people and the

government officials, thereby enhancing the naxal activities in forests.

Class 10th Science Chapter 16 Intext Questions Page No. 276

Question 1.
Find out about the traditional systems of water harvesting/ management in your region.
We must dug small pits and lakes, put in place simple water shed systems, built small earthen dams, constructed dykes, sand and limestone reservoirs, set up root top water collecting units. These are the traditional systems of water harvesting/management in our region.

Question 2.
Compare the above system with the probable systems in hilly/ mountainous areas or plains or plateau regions.
In the above mentioned places check dams are built because here water harvesting is difficult.

Question 3.
Find out the source of water in your region/locality. Is water from this source available to all people living in that area?
Tube wells and river water (Tungabhadra) are the water sources available to all people in our area. There are different sources in different places. In some places there is too much shortage of water because of failure of rain recently.

### MP Board Class 10th Science Chapter 16 NCERT Textbook Exercises

Question 1.
What changes would you suggest in your home in order to be environment-friendly?
Changes that can be undertaken in our homes to be environment friendly are listed below:

1. Switch off the electrical appliances when not in use.
2. Turn the taps off while brushing or bathing and repair the leaking taps.
3. Throw biodegradable and non-biodegradable waste into separate bins.
4. Construct composting pits.
5. Food items such as jam, pickles etc., come packed in plastic bottles. These bottles can later be used for storing things in the kitchen.

Question 2.
Can you suggest some changes in your school which would make it environment-friendly?
Changes that can be undertaken in our schools to make it environment friendly are listed below:

1. Electricity can be saved by switching off lights and fans when not required.
2. Turn the taps off when not in use.
3. Biodegradable and non-biodegradable wastes should be thrown into separate bins.

Question 3.
We saw in this chapter that there are four main stakeholders when it comes to forests and wildlife. Which among these should have the authority to decide the management of forest produce? Why do you think so?
The forest department of the government should have the authority to decide the management of forest produces. This is because the forest department is the care taker of the forest land and is responsible for any damage to the forest.

Question 4.
How can you as an individual contribute or make a difference to the management of
(a) forests and wildlife
(b) water resources and
(c) coal and petroleum?
a) Forests and wild animals.

1. cutting valuable trees should be avoided by destroying forest affects the quality of soil and water resources.
2. Hunting should be prohibited.
3. There should be wild sanctuaries which gives protection for wild animals.

b) Water Resources:

1. Water resources should be free from pollution.
2. Excess usage of water should be avoided.

c) Coal and Petroleum:
We should minimise the use of coal and petroleum, because these are fossil fuels. By burning these there are ill effects such as air pollution and acid rainfall etc.

Question 5.
What can you as an individual do to reduce your consumption of the various natural resources?

1. We must have come across the five R’s to save the environment: Refuse, Reduce, Reuse, Repurpose and Recycle.
2. We should encourage tree plantation programmes.
3. We must reduce the burning of fossil fuels.
4. Encouragement should be given for harvesting the water.

Question 6.
List five things you have done over the last one week to —
(a) conserve our natural resources.
We should travel in bus instead of using own vehicles or we should practice walking, we must use LED bulbs or fluorescent tubes in our homes. We must use the lift or taking the stairs, wearing an extra sweater or using a heating device (heater or sign) on cold days.

(b) increase the pressure on our natural resources.

1. We should grow Number of trees around our house.
2. Reducing own vehicles by using public transport system or by, walking.
3. There should not be more factories.
4. We must prevent soil erosion.
5. We must reduce the usage of vehicles to avoid air pollution.

Question 7.
On the basis of the issues raised in this chapter, what changes would you incorporate in your lifestyle in a move towards sustainable use of our resources?
We need to change our lifestyles so that we can use natural resources on a sustainable basis. The changes which can be brought about are as follows:

• Stop cutting trees and start planting trees.
• Use LED bulbs and fluorescent tubes.
• Take the stairs and avoid using lifts.
• During summers use bamboo made fans avoid air coolers and electricians.
• Use more of public transport.
• Let our conscience be always alert not to pollute the environment from any of our activities.

### MP Board Class 10th Science Chapter 16 Additional Important Questions

MP Board Class 10th Science Chapter 16 Multiple Choice Questions

Question 1.
The three R’s to save the environment are:
(a) Reuse
(b) Reduce
(c) Recycle
(d) Reduce, recycle, reuse
(d) Reduce, recycle, reuse

Question 2.
Biodiversity is measured by
(a) The number of animals found in an area
(b) The number of mammalian found in an area
(c) The number of species found in an area
(d) The number of insects found in an area
(c) The number of species found in an area

Question 3.
What are biodiversity hot spot?
(a) Village
(b) River
(c) Cities
(d) Forests
(d) Forests

Question 4.
Harvesting system in hilly areas like Himachal Pradesh uses a local system of irrigation called
(a) Tals
(b) Canals
(c) Kulhs
(d) Ahass
(c) Kulhs

Question 5.
Amrita Devi Bishnoi sacrificed her life with 363 people in 1731 to save
(a) Wildlife
(b) Water
(c) Girl child
(d) Trees
(d) Trees

Question 6.
Aim of ‘Narmada Bachao Andolan’, was
(a) Stopping dam formation
(b) Stopping ban on dam formation
(c) Stopping water pollution
(d) Garbage maintenance
(a) Stopping dam formation

Question 7.
Coli form is
(a) Group ef fungi
(b) Group of viruses
(c) Group of bacteria
(d) All of these
(c) Group of bacteria

Question 8.
Main aim of the Chipko movement was:
(a) Water conservation
(b) Ecological conservation
(c) Food conservation
(d) All of the above
(b) Ecological conservation

Question 9.
Which gas is a green house gas?
(a) CO2
(b) CO
(c) SO2
(d) NO2
(a) CO2

Question 10.
The Chipko movement started in a village called
(a) Reni in Uttarakhand
(b) Kullu
(c) Delhi
(d) Mumbai
(a) Reni in Uttarakhand

Question 11.
Indira Gandhi canal is an example of:
(a) River
(c) Pond
(d) All of these

Question 12.
Kattas in Karnataka is famous for:
(a) Water harvesting
(b) Solar energy
(c) Biodiversity
(d) None
(a) Water harvesting

MP Board Class 10th Science Chapter 16 Very Short Answer Type Questions

Question 1.
Define natural resource.
The things available from nature are called natural resource.

Question 2.
Name the 3 R’s to save environment.
Reduce, recycle, reuse are the 3 R’s to save environment.

Question 3.
Give some examples of natural resources.
Examples of natural resources are water, timber and cotton.

Question 4.
What is biodiversity?
Biodiversity is number of species that exists in an area.

Question 5.
What increases demand of resources?
Increase in human population increases demand of resources.

Question 6.
Why we should need to manage our resources? Give one example.
We need to manage our resources for equitable distribution for every individual.

Question 7.
Give one example of stakeholder of forest.
People who live in or around forest are best example of stakeholder of forest.

Question 8.
In which village Chipko movement was started?
Chipko movement started in Reni village in Uttarakhand.

Question 9.
What was the main purpose of Chipko andolan?
To stop tree cutting indiscriminately.

Question 10.
What are the alternative sources to produce energy without creating pollution and disturbing ecological balance?
Sunlight, water, wind etc.

Question 11.
Can we recycle everything?
No, because everything do not turn in usable form once being used.

Question 12.
What is an example of biodiversity hot spot?
Forest.

Question 13.
Write an importance of conservation of wild life.
Preserving biodiversity inherited in time.

Question 14.
Write name of one activist for saving water.
Rajendra Kumar.

Question 15.
Give an example of a place famous for water management in India.
Kulhs in Himachal Pradesh.

MP Board Class 10th Science Chapter 16 Short Answer Type Questions

Question 1.
What are natural resources? Explain.
Natural resources can be broadly categorized into two types: exhaustible and non-exhaustible. Management of natural resources is all about their judicious use in a way that the exhaustible resources can lasfr.for many generations to come and non-exhaustible resources can be maintained in as pristine form as possible.

Question 2.
What are three R’s (Reduce, recycle and reuse)?
Reduce: We should reduce the consumption of various resources wherever possible. For example; we can reduce the consumption of electricity and water.

Recycle: There are many items which can be recycled again and again. For example by recycling paper, we reduce the demand for wood and thus, help in saving the forest.

Reuse: Many items can be reused many times. For example; old newspaper, envelopes, plastic bottles.

Question 3.
Who are the stakeholders of forest?
The stakeholders are as follows:
People living in or around forests; as they depend on various forest produce for their livelihood, the forest department which is the owner of the forest land, various industrialists who depend on forest for many raw materials. For example: wood is used as raw material in many industries.

So, the people, industry and Government body who are directly or indirectly affected by forest are called stakeholders of forest.

Question 4.
Give one example of saving ecosystem by local communities.
Chipko Movement: The Chipko movement began in the early 1980s from a small village; Reni in Garhwal district. The women of the village began hugging the trees to prevent the cutting of trees by the contractors. The Chipko movement later spread to other parts of India.

Question 5.
Give some examples of water harvesting method in ancient India.

1. Khadins, tanks and nadis in Rajasthan.
2. Bandharas and tals in Maharashtra.
4. Ahars and pynes in Bihar.
5. Kulhs in Himachal Pradesh.
6. Ponds in the Kandi belt of Jammu region and eris (tanks) in Tamil Nadu. Surangams in Kerala, and Kattas in Karnataka.

These are some of the ancient water harvesting examples and still in use at many places.

Question 6.
What is the importance of traditional water harvesting structures?
The traditional water harvesting structures usually focus on recharging the groundwater rather making an open reservoir. It has several advantages. Unlike surface water; the groundwater does not evaporate and»thus, loss because of evaporation is prevented. The groundwater does not provide a breeding ground for the mosquitoes and hence is good for public health as well. The groundwater is relatively protected from contamination by human activities.

Question 7.
Why alternate energy sources is required in place of Coal and Petroleum? Give examples of alternate sources.
Coal and petroleum are the main energy resources for us. But, since these are exhaustible in nature so, we need to find out alternate sources of energy. Scientists are working on developing some alternate energy sources so that dependency on coal and petroleum can be reduced. Some examples are given below:

1. Solar energy is being used to produce electricity at many places. Although, this technology is still costly.
2. Fuel cell is another development which may help in replacing the internal combustion engines from automobiles.
3. Hydrogen is being used as fuel in buses and cars in many countries. Hydrogen; when used as a fuel produces water as a by-product. Thus, hydrogen can be an environment-friendly fuel.

MP Board Class 10th Science Chapter 16 Long Answer Type Questions

Question 1.
Explain consequences of exploitation of natural resources and sustainable development.
There are many consequences of exploitation of natural resources.
Some examples are given below:

1. Burning of fossil fuels creates air pollution. Excess amount of carbon dioxide in the atmosphere leads to global warming.
Some polluting gases; like oxides of nitrogen and sulphur lead to acid rain, which is harmful for living beings. Acid rain is also harmful for monuments and buildings.
2. Excess exploitation of groundwater leads to a drastic fall in water table. For this reason many places are experiencing acute shortage of drinking water.
3. Overuse of fertilisers and insecticides leads to soil pollution and soil erosion.
4. Many pollutants are directly flown into water bodies. This has resulted in water pollution in many rivers, lakes and even in oceans.

Sustainable Development:

Development is necessary for making all around economic development. But development often comes with a price in the form of environmental damage. Sustainable development means following certain practices which help in saving our environment from damage. This is necessary for maintaining the earth in a good shape so, that future generations can also enjoy bounty of nature.

Question 2.
What are three R’s?
1. Reduce: We should reduce the consumption of various resources wherever possible. For example; we can reduce the consumption of electricity by switching off lights and other appliances when they are not required. While leaving the home, one should always check for fans and lights and switch them off. This cannot only help in saving electricity but also in saving the fuels which are utilised in electricity production. We should immediately repair a leaking tap so that precious water can be saved.

2. Recycle: There are many items which can be recycled again and again. Recycling is another way of reducing the demand for natural resources. For example; by recycling paper, we reduce the demand for wood and thus, help in saving the forest.

3. Reuse: Many items can be reused many times. For example; old newspaper can be used for packing many items. Old envelopes can be used, for doing rough work while doing homework. Old plastic bottles can be used for many other purposes.

Question 3.
Explain Arabari’s example of People’s Participation in Forest Management.
In 1972, the forest department realized its mistake while reviving the degraded sal forests of Arabari forest range. Arabari forest lies in Midnapore district of West Bengal. The earlier methods of policing and surveillance were a total failure as they often led to frequent clashes with local people. It also led to alienation of people from the conservation programme. Then, came a forest officer; named A.K Baneijee; who was a real visionary. He involved the local people in the revival of 1,272 hectares of forest. In lieu of that the villagers were given employment in silviculture and were given 25% of the harvest. They were also allowed to gather firewood and fodder against a nominal payment. Due to active participation of the local community, there was remarkable revival of the Arabari sal forest. By 1983, the value of the forest rose to ? 12.5 crores.

Question 4.
Explain in brief about people ‘effort for forest conservation’.
Bishnoi community: The Bishnoi community of Rajasthan is one such example. Amrita Devi Bishnoi is still remembered with reverence for the way she fought for protecting the khejri trees in Khejrali village. She along with 363 other people sacrificed her life for the protection of khejri trees in 1731. The ‘Amrita Devi Bishnoi National Award for Wildlife Conservation’ has been named in her honour.

Nomadic herders of the Himalayas: The nomadic herders used to graze their animals near the great Himalayan National Park. Every summer, the nomadic people brought their herds down the valley so that the sheep could get plenty of grass to eat. When the National Park was made in that area, the nomadic herders were stopped from grazing their sheep in the protected area. Now, in the absence of grazing by the sheep, the grasses grew very tall in the region. Tall grasses fall over and prevent fresh growth of grass. This shows that by excluding and alienating the local people from forests, proper conservation efforts cannot be carried out.

Chipko movement: The Chipko began in the early 1980s from a small village; Reni in Garhwal district. The women of the village began hugging tree to prevent the cutting of trees by the contractors. The Chipko movement later spread to other parts of India.

Question 5.
Give two examples of forest conservation by local communities.
Following are two examples of Forest conservation by local
communities:

1. The Chipko movement began in the early 1980s from a small village; Reni in Garhwal district. The women of the village began hugging a tree to prevent the cutting of trees by the contractors. There are many examples which suggest that involvement of local communities is necessary for any conservation effort. The Bishnoi community of Rajasthan is one such example. Amrita Devi Bishnoi is still remembered with reverence for the way she fought for protecting the khejri trees in Khejrali village. She along with 363 other people, sacrificed her life for the protection of Khejri trees in 1731. The ‘Amrita Devi Bishnoi National Award for Wildlife Conservation’ has been named in her honour.

2. Another example is of the nomadic herders of the Himalayas. The nomadic herders used to graze their animals near the great Himalayan National Park. Every summer, the nomadic people bought their herds down the valley so that the sheep could get plenty of grass to eat. When the National Park was made in that area, the nomadic herders were stopped from grazing their sheep in the protected area. Now in the absence of grazing by the sheep, the grasses grew very tall in the region. Tall grasses fall over and prevent fresh growth of grass. This shows that by excluding and alienating the local people from forests, proper conservation efforts cannot be carried out.

### MP Board Class 10th Science Chapter 16 NCERT Textbook Activities

Class 10 Science Activity 16.1 Page No. 266

• Find out about the international norms to regulate the emission of carbon dioxide.
• Have a discussion in class about how we can contribute towards meeting those norms.

Observations:

• There are many laws and norms made to regulate the emission of various gases that creates harm to the environment. One of the norms related to CO2 emission is based on ‘Kyoto protocol’ where all industrialised countries come forward to minimize the collective emission of CO2 and other green house gases.

Class 10 Science Activity 16.2 Page No. 267

• There are a number of organisations that seek to spread awareness about our environment and promote activities and attitudes that lead to the conservation of our environment and natural resources. Find out about the organisations(s) active in your neighbourhood/village townicity.
• Find out how you can contribute towards the same cause,

Observations:

• There are many organisations spreading awareness about environment and promoting activities for its benefit. Different states of India have number of organisations. The name of new includes – Ionosphere Social Enterprise, The energy and resonance Institute IRADe, Elnora International, Delhi Greens, Greenpeace India, GVNMAL, India Nateere watch, Kalpvriksh. Nation’s club. National biodiversity Authority etc.

Class 10 Science Activity 16.3 Page No. 266

• Check the pH of the water supplied to your house using universal indicator or litmus paper.
• Also check the pH of the water in the local waterbody (pond, river, lake, stream).
• Can you say whether the water is polluted or not on the basis of your observations?

Observations:

• The normal range for pH in our house may be between 6.5 to 8.5. The pH of local water bodies are around 5.7.
• The water showing little less pH than recommended in water bodies may indicate pollution due to slight acidic substances which make the water acidic showing decrease in pH.
• The optimum range for water bodies in around 6-8.5, the variations in it indicates pollutions.

Class 10 Science Activity 16.4 Page No. 269

• Have you ever visited a town or village after a few years of absence? If so, have you noticed new roads and houses that have come up since you were there last? Where do you think the materials for making these roads and buildings have come from?
• Try and make a list of the materials and their probable sources.
• Discuss the list you have prepared with your classmates. Can you think of ways in which the use of these materials be reduced?

Observations:

• Yes, new roads and houses are coming up very fastly in villages. The materials generally comes from the neighbouring cities and areas where it is build.
• The materials for building roads and buildings includes concrete, composite pavement, asphalt, bituminous, gravel surfaces etc.
• These can be reduced by opting for less toxic and dangerous materials like bituminous and asphalt may be avoided and replaced by sand and naturally made materials.

Class 10 Science Activity 16.5 Page No. 270

• Observe various traditional practices for conservation of nature in your day-to day life. Share within the peer group. Make a report and submit.

Observations:

• Various traditional practices for conservation of nature includes various practices like:
• Religious traditions – temple forest, monastery forests etc.
• Traditional tribal traditions – sacred forests, sacred trees etc.
• Royal traditions – royal hunting practices and preserves, royal gardens etc.
• Livelihood traditions – forests and grows serving as cultural and social space.

Class 10 Science Activity 16.6 Page No. 271

• Make a list of forest produce that you use.
• What do you think a person living near a forest would use?
• What do you think a person living in a forest would use?
• Discuss with your classmates how these needs differ or do not differ and the reasons for the same.

Observations:

• Forest produce that are use includes:
• Wood, sandalwood, rubber, latex, paper, food (fruits and vegetables), Sponges, wood fuel etc.
• A person living near a forest will use wood as fuel, fruits and Vegetables, rubber, sandal cored etc.
• A person leaving in a forest will decrease the storage of forest produce and can used hand in hand as and when required. The use of many things will reduce.
• The person living near will have different requirements as compared to person duriug-inside forest as maximum needs of people living in forest wall increase as he can directly take from there neither than cutting or taking from native and then utilising

Class 10 Science Activity 16.7 Page 272

• Find out about any two forest produce that are the basis for an industry.
• Discuss whether this industry is sustainable in the long run. Or do we viced to control our consumption of these products?

Observations:

• Any two forest produce that are basis for an industry arc wood and coal.
• This industry is not sustainable in the long run as the limited supply for these products are available in nature and we are using them at very high speed. We need to reduce the consumption and wastage of such products. The natural resources should be used judiciously.

Class 10 Science Activity 16.8 Page No. 275

• Debate the damage caused to forests by the following:
• (a) Building rest houses for tourists in national parks.
• (b) Grazing domestic animals in national parks.
• (c) Tourists throwing plastic bottles, covets and other litter in national parks.

Observations:

• The building rest houses for tourists in national parts causes a lot increase in deforestation which disturbs the balance of the nature. The animals and other living organisms living in an ecosystem also gets disturbed and whole area is effected.
• Grazing domestic animals leads to destruction of green grasses and shrubs which destroy the green cover of the park. This also effects the other dependent organisms of the park.
• The plastic bottles/covers and other litter thrown in the national parks makes the park very dirty making it unfit in providing healthy living conditions to the animals. These substances do not decompose and remain there creating pollution for years and leading to destruction of various organisms.

Class 10 Science Activity 16.9 Page No. 275

• Villages suffering from chronic water shortage surround a water theme park in Maharashtra. Debate whether this is the optimum use of the available water.

Observations:

• No, this is not the optimum use of the available water. Water theme park in Maharashtra uses water in large animals for the amusement purposes. This water can be used for various other basic needs. There is acute shortage of water in nearby areas. This water can fulfill the needs there.

Class 10 Science Activity 16.10 Page No. 275

• Study the rainfall patterns in India from an atlas.
• Identify the regions where water is abundant and the regions of water scarcity.

Observations:

• The monsoon affect the most part of India, the amount of rainfall varies from heavy to scanty in different parts. There is great temporal and regional variation in distribution of rainfall. Over 80% of annual rainfall is received in four rainy months of June to September.
• The regions with abundant water includes – most of Canada, Great Lakes, Ireland, Amazon (Brazil), Antarctica.
• The regions of water scarcely includes – Middle East, Sahara Desert, Atacama Desert, India, Gobi Desert

Class 10 Science Activity 16.11 Page No. 279

• Coal is used in thermal power stations and petroleum products like petrol and diesel are used in means of transport like motor vehicles, ships and aeroplanes. We cannot really imagine life without a number of electrical appliances and constant use of transportation. So can you think of ways in which our consumption of coal and petroleum products be reduced?

Observations:

• We can reduce our consumption of coal and petroleum by using other means of energy like solar, hydral, wind and various other natural forms of energy. These sources are renewable and do not cause any harm to the nature.

Class 10 Science Activity 16.12 Page No. 279

• You must have heard of the euro I and Euro II norms for emission from vehicles; Find out how these norms work towards reducing air pollution.

Observations:

• Euro norms refer to the permissible emission levels from both petrol and diesel vehicles. They are available for fuel quality and the method of testing. These norms decides how much a can should smoke and the particles emitted out. It have been in Europe first and then it was also implemented in India as well in the name of Bharat stage I and II.

## MP Board Class 10th Science Solutions Chapter 15 Our Environment

### MP Board Class 10th Science Chapter 15 Intext Questions

Class 10th Science Chapter 15 Intext Questions Page No. 257

Question 1.
Why are some substances biodegradable and some non- biodegradable?
Some substances can be broken down into simpler substances by the action of enzymes and other physical factors and are returned to the earth. Some substances cannot be degraded into simpler form and exists in nature for very long, deteriorating it and hence, are termed as non- biodegradable.

Question 2.
Give any two ways in which biodegradable substances would affect the environment.

1. These substances may cause pollution the environment.
2. They may serve breeding ground for pathogens which may cause diseases

Question 3.
Give two ways in which non-biodegradable substances would affect me environment.

1. They do not degrade and pile up in the environment causing harm to the ecosystem.
2. They may lead to bio-magnification in food chain disturbing the various trophic levels.

Class 10th Science Chapter 15 Intext Questions Page No. 261

Question 1.
What are the trophic levels? Give an example of a food chain and state the different trophic levels in it.
Each step or level of a food chain is called Trophic levels.
Example for Food chain – Here grass is a producer because it prepares its own food. This grass is eaten by herbivores means secondary, small carnivores (Frog) are tertiary and higher carnivores are in the fourth level.

Question 2.
What is the role of decomposers in the ecosystem?
Microorganisms, comprising bacteria and Fungi, break-down the dead remains and waste products of organisms. These microorganisms are the decomposers as they break-down the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants.

Class 10th Science Chapter 15 Intext Questions Page No. 264

Question 1.
What is ozone and how does it affect any ecosystem?
Ozone at the higher levels of the atmosphere is a product of UV radiations acting on O2 molecule. The higher energy UV radiations split apart some molecular Oa in free oxygen (O) atoms. These atoms then combine with the molecular O2 to form Ozone.

Ozone shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms for example, it is known to cause skin cancer in human beings.

Question 2.
How can you help in reducing the problem of waste disposal? Give any two methods.

1. We must minimise the usage of plastics,
2. We can collect wastes and by this we can produce gas which is an alternate source of energy.

Class 10th Science Chapter 15 Ncert Textbook Exercises

Question 1.
Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
(a), (c), (d)

Question 2.
Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
(b) Grass, goat and human

Question 3.
Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
(d) All of the above

Question 4.
What will happen if we kill all the organisms in one trophic level?
If we kill all the organisms in one trophic level, the population size of organisms in lower level increases uncontrollably and the number of organisms in higher trophic level decreases due to non¬availability of food. This results in an imbalance in ecosystem.

Question 5.
Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?

• Removing producers: All the heterotrophs die.
• Removing herbivores: Carnivores would not get food.
• Removing carnivores: Herbivores would increase to unsustainable levels.
• Removing decomposers: Organic wastes, plant, and animal dead remains would pile up.
• The role of each and every species belonging to every trophic level is unique.
• No, the organisms of any trophic level cannot be removed without damaging the ecosystem.

Question 6.
What is the biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Some harmful chemicals enter our bodies through the food chain, one of the reasons is the use of several pesticides and other chemicals to protect our crops from disease and pests. These chemicals are either washed down into the soil or into the water bodies. From the soil, these are absorbed by the plants along with water and minerals and from the water bodies these are taken up by aquatic plants and animals.

This is one of the ways in which they enter the food chain. This phenomenon is known as biological magnification. This level of magnification be different at different levels of the ecosystem.

Example; Spraying of DDT will remain for a long time in the environment.

Question 7.
What are the problems caused by the non-biodegradable wastes that we generate?

• Non-aesthetic look.
• Death of cattle by ingestion of plastic bags.
• The quality of soil is adversely affected.
• Biomagnification of harmful chemicals like DDT in birds disturb their calcium metabolism.
• Non – biodegradable wastes cause pollution of soil and water.

Question 8.
If all the waste we generate is biodegradable, will this have no impact on the environment?
If all the waste we generate is biodegradable, there is a imbalance in nature. Because with the increase of wastes there is decrease in the number of decomposers. These wastes spread every where and microbes are more which causes many diseases to us.

Question 9.
Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Damage to the ozone layer causes so many problems. At the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet radiation from the sun. If ozone layer is damaged no organism can survive. The following are the steps being taken to limit this damage.

1. We should minimize the use of vehicles.
2. We should not encourage the burning of fossilic fuels.
3. It is now mandatory for all the manufacturing companies to make CFC- free refrigerators throughout the world.

### MP Board Class 10th Science Chapter 15 Additional Important Questions

MP Board Class 10th Science Chapter 15 Multiple Choice Questions

Question 1.
An environment consists of:
(a) Abiotic components
(b) Biotic components
(c) Both
(d) Not certain
(c) Both

Question 2.
Waste could be:
(a) Abiotic components
(b) Biotic components
(c) Both
(d) Not certain
(c) Both

Question 3.
Reduction of waste is important to:
(a) Make environmental balance proper.
(b) Make nearby beautiful
(c) waste can be transformed to useful products.
(d) Not clear
(d) Not clear

Question 4.
Which one among following is non-biodegradable substance?
(a) Metal
(b) Wood
(c) Water
(d) Urea
(a) Metal

Question 5.
Which among the following is a biodegradable waste?
(a) Wood
(b) Teflon pots
(c) Plastic cup
(d) Glass Cups
(a) Wood

Question 6.
Most convenient ways of waste management is:
(a) 3 R : Reduce, reuse, recycle principle
(b) Production
(c) Use ban
(d) None
(a) 3 R : Reduce, reuse, recycle principle

Question 7.
Which one is not a primary consumer?
(a) Grasshopper
(b) Deer
(c) Ant
(d) Leech
(b) Deer

Question 8.
Humans are:
(a) Primary consumers
(b) Secondary consumers
(c) Top consumers
(d) All
(d) All

Question 9.
Energy while going up in a trophic level is:
(a) Increased
(b) Decreased
(c) Remain same
(d) Can’t predict
(b) Decreased

Question 10.
Pesticides are used to:
(a) Develop new varieties of crops.
(b) Kill unwanted plants.
(c) Kill insects and enrobes attacking crops.
(d) Save crops from birds.
(c) Kill insects and enrobes attacking crops.

Question 11.
In a marine ecosystem producers are:
(a) Plants
(b) Sand
(c) Water
(d) Fishes
(d) Fishes

Question 12.
Top consumer in a crop field is:
(a) Rat
(b) Hawk
(c) Snake
(d) (a) and (b)
(b) Hawk

Question 13.
Effect of bio-magnification is maximum in:
(a) Primary consumers
(b) Secondary consumers
(c) Top consumers
(d) All of these
(c) Top consumers

Question 14.
Which one of the following is artificial ecosystem?
(a) Jungle
(b) Town
(c) A pond
(d) Mountain
(b) Town

Question 15.
Cockroach is a:
(a) Producer
(b) Primary consumer
(c) Secondary consumer
(d) Decomposer
(d) Decomposer

Question 16.
Energy source of an ecosystem is:
(a) Producers
(b) Sunlight
(c) Top consumer
(d) Atmospheric gases
(b) Sunlight

Question 17.
Link between primary and secondary consumers are:
(a) Autotrophs
(b) Omnivorous
(c) Carnivorous
(d) Herbivorous
(a) Autotrophs

Question 18.
What is CFC?
(a) A waste
(b) A coolant gas
(c) A bakery product
(d) An organization
(b) A coolant gas

Question 19.
UNEP stands for:
(a) United Nations Environment Programme.
(b) United Nations Entertainment Programme.
(c) United Nations Excellence Programme.
(d) Unlimited Nations Excellence Programme.
(a) United Nations Environment Programme.

Question 20.
How many atoms of oxygen compose an ozone molecule?
(a) 1
(b) 2
(c) 3
(d) 4
(c) 3

MP Board Class 10th Science Chapter 15 Very Short Answer Type Questions

Question 1.
Which gas of our environment help in formation of energy which we get from various sources?
Oxygen.

Question 2.
How non-biodegradable objects effect environment?
They pollute the environment.

Question 3.
Name two substances you think as most non-biodegradable.
Plastic and chemicals like pesticides.

Question 4.
Which organisms help in biodegradation of a substance?
Decomposers.

Question 5.
Write three common waste produced by our daily use.
Soap and detergent, consumed food materials used paper and plastic garbage.

Question 6.
Can a big tree be treated as an isolated small ecosystem?
Yes.

Question 7.
Give examples of natural ecosystem.
Forests, pond, river etc.

Question 8.
Give examples of artificial ecosystem.
Aquariums, Garden, town etc.

Question 9.
Can a ecosystem survive without autotrophs?
No.

Question 10.
At which category parasite come in an ecosystem?
Decomposers.

Question 11.
At which level rabbit and mole come in trophic level?
Rabbit – Primary level.
Mole – Primary and decomposer level.

Question 12.
How much percentage of sunlight is converted into chemical energy by all autotrophs?
1 %.

Question 13.
What percentage of average organic matter is present at each step of trophic level?
10%.

Question 14.
What kind of plants comes at primary consumers level?
Carnivorous plants.

Question 15.
How many minimum food chains can be observed in a food web?
2 – 3.

MP Board Class 10th Science Chapter 15 Short Answer Type Questions

Question 1.
What is ecosystem? What are components of ecosystem?
An ecosystem includes all of the living things in a given area, interacting with each other and also with their non-living environments.

Components of ecosystem:
An ecosystem has two types of components – biotic component (plants, animals and organisms) and abiotic component (weather, earth, sun, soil, climate, atmosphere).

Question 2.
What is abiotic component?
All the non-living things make the abiotic component of an ecosystem. Air, water and soil are the abiotic components.

Question 3.
What is the importance of abiotic component?
Air provides oxygen (for respiration), carbon dioxide (for photosynthesis), water (for metabolic activities) and soil is the reservoir of various nutrients which are utilized by plants. Through plants; these nutrients reach other living beings.

Question 4.
What is a biotic component?
Ail living beings make the biotic component of an ecosystem. Examples: Green plants, animals and other living beings. Bacteria and fungi are examples of biotic component.

Question 5.
What is a food chain?
A food chain is a simple representation of transfer of energy from the sun to different biotic components of an ecosystem. Sun is the ultimate source of energy. Green plants convert solar energy into chemical energy during photosynthesis. When an animal takes food, this energy is supplied to the animal and the process goes on.

Question 6.
What is food web and trophic level?
Food web: In an ecosystem, there can be many food chains which are interlinked at various levels. Thus, many food chains form a network which is called food web.

Trophic level: Transfer of energy occurs through a food chain. Different levels in the food chain are called trophic level.

Question 7.
What are biodegradable substances?
Substances which can be decomposed by microorganisms are called biodegradable substances. All the organic substances are biodegradable.

Question 8.
What are non-biodegradable substances?
Substances which cannot be decomposed by microorganisms are non biodegradable. All inorganic substances are non-biodegradable. Many synthetic substances are also non biodegradable.

Question 9.
Give two differences between biodegradable and non bio-degradable.

Question 10.
What is ozone layer? How it is protected from ultraviolet radiations?
Ozone layer is also known as stratosphere. When ultraviolet radiations act on oxygen, the oxygen gets converted into ozone. Ozone layer works like a protective shield for living beings. The ozone layers guards from harmful ultraviolet rays of the sun.

MP Board Class 10th Science Chapter 15 Long Answer Type Questions

Question 1.
What is ecosystem? Explain in detail the components of ecosystem.
An ecosystem includes all of living things in a given area, interacting with each other and also with their non living environments.

Components of ecosystem:

1. Biotic component (plants, animals and organisms) and abiotic components (weather, sun, soil, climate, atmosphere).
All living beings make the biotic component of an ecosystem. Examples: Green plants, animals and other living beings. Bacteria and fungi are examples of biotic component.

Green plants play the role of producers: Because they prepare the food by photosynthesis.

Animals and other living beings play the role of consumers; because they take food (directly or indirectly) from plants.

Bacteria and fungi play the role of decomposers; as they decompose dead remains of plants and animals so that raw materials of organisms can be channelized back to the environment.

2. Abiotic component: All the non-living things make the abiotic component of an ecosystem. Air, water and soil are the abiotic components.

Air provides oxygen (for respiration), carbon dioxide (for photosynthesis) and other gases for various needs of the living beings.

Water is essential for all living beings because all the metabolic activities happen in the presence of water.

Soil is the reservoir of various nutrients which .are utilized by plants. Through plants, these nutrients reach other living beings.

Question 2.
Explain in briefly about food chain.
A food chain is a simple representation of transfer of energy from the sun to different biotic components of an ecosystem. Sun is the ultimate source of energy. Green plants convert solar energy into chemical energy during photosynthesis. When an animal takes food, this energy is supplied to the animal and the process goes on. A simple food chain can be shown as follows:

Producer → Primary consumer → Secondary consumer

Real life cannot be as simple as a food chain shown above. In any ecosystem, there can be many food chains which are interlinked at various levels. Thus, many food chains form a network which is called food web.

Transfer of energy occurs through a food chain. Different levels in the food chain are called trophic level. Out of the energy consumed by an organism at a particular trophic level, 90% is utilized for its own need and rest 10% is left for the organism of the next trophic level. So. very little energy is tell for the organism which is at the tertiary level. Letus assume that a green plant makes 100% energy in the form of chemical energy, 90% of this energy would be utilized for its own purpose. This would leave just 10% energy for the primary consumer. Now, primary consumer shall also utilize 90% of energy which was consumed by it. This would leave just 1% energy for (10% of 100%) for the secondary consumer. By this logic, the tertiary consumer would get just 0.1% of energy which was originally made by the green plant. This is the reason, there can be just one or two organisms at the top of the food pyramid.

This explains why the population of producers is always the largest in an ecosystem; followed by the population of herbivores and then that of carnivores. Moreover, herbivores needs to eat many plants in its lifetime to fulfill its energy need. Similarly, carnivores needs to eat many herbivores in its lifetime.

Question 3.
What is ozone layer depletion?
Ozone layer is also known as stratosphere. When ultraviolet radiations act on oxygen, the oxygen gets converted into ozone.

Ozone layer works like a protective shield for living beings. The ozone layers guards from harmful ultraviolet radiations from the sun.

Effect of CFCs: Use of CFCs (Chlorofluorocarbon) has damaged the ozone layer. As a result, the ozone layer has become thinner at certain parts. In 1987, the UNEP (United Nations Environment Programme) succeeded in forging an agreement among different nations to freeze the CFC production at 1986 level. Later, an agreement was signed among different nations to phase out CFCs. It is important to note that CFC is used in refrigerators and aerosol sprays. India is also a signatory of that agreement and thanks to the efforts by the United Nations and different environmentalists, the CFC emission has been put under some control.

Problems of waste disposal: During our day to day activities, we produce lot of waste. While some of the waste is biodegradable, a large chunk is composed of non-biodegradable substances. Plastic waste is a serious concern because plastic is non-biodegradable. We need to respect our environment and find out ways to reduce the burden on our environment.

### MP Board Class 10th Science Chapter 15 NCERT Textbook Activities

Class 10 Science Activity 15.1 Pages No. 256,257

• You might have seen an aquarium. Let us try to design one.
• What are the things that we need to keep in mind when we create an aquarium? The fish would need a free space for swimming (it could be a large jar), water, oxygen and food.
• We can provide oxygen through an oxygen through an oxygen pump (aerator) and fish food which is available in the market.
• If we add a few aquatic plants and animals it can become a self- sustaining SySieni.’ Can you think how this happens? An aquarium is an example of a human-made ecosy stem.
• Can we leave the aquarium as such after we set it up?
• Why does it have to be cleaned once in a while? Do we have to clean ponds or lakes in the same manner? Why or why not?

Observations:

• Pesticides are the chemicals sprayed to kill the pests infecting crop and harming them. These are very harmful to living organisms. These get biologically magnified in the food chains and in the bodies, once entered. Organic farming methods and other natural methods can be adopted to reduce dependence on chemicals.

Class 10 Science Activity 15.2 Page No. 257

• While creating an aquarium did you take care not to put an aquatic animal which would eat others? What would have happened otherwise?
• Make groups and discuss how each of the above groups of organisms are dependent on each other.
• Write the aquatic organisms in order of who eats whom and form a chain of at least three steps.
• Would you consider any one group of organisms to be of primary importance? Why or why not?

Observations:

• CFC’s are responsible for depletion of ozone layer.
• These chloroflouro carbons were banned in various countries and since, then ozone hole has decreased in size.

FIg. 15.1: Food chain ¡n nature (a) in forest, (b) in grassland and (c) in pond.

Class 10 Science Activity 15.3 Pages No. 244,245

• Newspaper reports about pesticide levels in ready made food items are often seen these days and some states have banned these products. Debate in groups the need for such bans.
• What do you think would be the source of pesticides in these food items? Could pesticides get into our bodies from this source through other food products too?
• Discuss what methods could be applied to reduce our intake of pesticides.

Observations:

• The materials that are non-biodegradable do not degrade easily. The hard materials that are not organic in nature take more time to decompose. The biodegradable materials turns soft and start decomposing and mixing in the soil. They completely change their form and structure.
• The waste from plants – fruits and vegetables change the fastest.

Class 10 Science Activity 15.4 Page No. 248

• Find out from the library, internet or newspaper reports, Which chemicals are responsible for the depletion of the ozone layer.
• Find out if the regulations put in place to control the emission of these chemicals have succeeded in reducing the damage to the ozone layer. Has the size of the hole in the ozone layer changed in recent years?

Observations:

• CFCs, SO2 other pollutant gases are responsible for the depletion of ozone layer.
• Non-biodegradable materials take years to decompose. Plastics are generally non-biodegradable and not decompose. The materials like paper, jute etc. easily degrade and do not harm the environment.

Class 10 Science Activity 15.5 Page No. 249

• Collect waste material from your homes. This could include all the waste generated during a day, like kitchen waste (spoils food, vegetable peels, used tea leaves, milk packets and empty cartons), waste paper, empty medicine bottles/strips/ bubble packs, old and tom clothes and broken footwear.
• Bury this material in a pit in the school garden or it there is no space available, you can collect the material in an old bucket/flower pot and cover with at least 15cm of soil.
• Keep this material moist and observe at 15-day intervals,
• What are the materials which change their form and structure over time?
• Of these materials that are changed, which ones change the fastest.1?”

Observations:

• We cannot leave the aquarium as it is as waste is generated in it by fishes which need to be cleaned up frequently so that it does not become toxic and harm the living organisms. The water bodies should also be cleaned up properly to ensure better living conditions. The aquatic life is affected by such kind of pollutions.

Class 10 Science Activity 15.6 Pages No. 249-250

• Use the library or Internet to find out more about biodegradable and non-biodegradable substances.
• How long are various non-biodegradable substances expected to last in our environment?
• These days, new types of plastics which are said to be biodegradable are available. Find out more about such materials and whether they do or do not harm the environment.

Observations:
Phytoplankton → Zoo planktons → Small fishes → Large fishes Aquatic Food Chain

• Phytoplankton are the autotrophs present in the water body and are of prime importance.
• The removal of any one group from the food chain will disturb the whole aquatic ecosystem.

Class 10 Science Activity 15.7 Page No. 252

• Find out what happens to the waste generated at home. Is there a system in place to collect this waste?
• Find out how the local body (Panchayat, municipal corporation, resident welfare association) deals with the waste. Are there mechanisms in place to treat the biodegradable and non-biodegradable wastes separately?
• Calculate how much waste is generated at home in a day.
• How much of this waste is biodegradable?
• Suggest ways of dealing with this waste.

Observations:

• The waste generated at home are differentiated into biodegradable and non-biodegradable materials. They are placed separately in the bins and thereafter, processed.

Class 10 Science Activity 15.8 Page No. 253

• Find out how the sewage in your locality is treated. Are there mechanisms in place to ensure that local water bodies are not polluted by untreated sewage?
• Find out how the local industries in your locality treat their wastes. Are there mechanisms in place to ensure that the soil and water are not polluted by this waste?

Observations:

• The amount of waste generated in homes and in the class-rooms is very high. At the end of the day. number of dustbins are fully filled which are thrown away in dump yard which too have become problematic. The wastes should be reused and amount generated should be reduced.

Class 10 Science Activity 15.9 Page No. 253

• Search the Internet or library to find out what hazardous materials have to be dealt with while disposing of electronic items. How would these materials affect the environment?
• Find out how plastics are recycled. Does the recycling process have any impact on the environment?

Observations:

• ETP (Effluent treatment plant) or STP (Sewage treatment plant) are used to treats the waste generated before it enters the water body. All the harmful treatments are removed and level of the toxic materials are reduced.

Class 10 Science Activity 15.10 Page No. 253

• Search the Internet or library to find out what hazardous materials have to be dealt with while disposing of electronic items. How would these materials affect the environment?
• Find out how plastics are recycled. Does the recycling process have any impact on the environment?

Observations:

• Electronic items are very hazardous as they are non-biodegradable and increase the mars on the earth.
• Plastic are recycled after melting again and-reforming into new shapes and products. This process create lots of pollution by emitting dangerous fumes and harms the environment.

## MP Board Class 10th Science Solutions Chapter 11 Human Eye and Colourful World

### MP Board Class 10th Science Chapter 11 Intext Questions

Class 10th Science Chapter 11 Intext Questions Page No. 190

Question 1.
What is meant by power of accommodation of the eye?
The ability of the eye to focus the distant objects as well as the nearby objects on the retina by changing focal length or converging power of its lens is called accommodation. The normal eye has a power of accommodation which enables the object as close as 25cm & as far as infinity to be focused on its retina.

Question 2.
A person with a myopic eye can not see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?
The person is able to see nearby objects clearly, but he is unable to see objects beyond 1.2m. This happens because the image of an object beyond 1.2 m is formed in front of the retina and not at the retina, as shown in the figure.

To correct this defect of vision, he must use a concave lens. The concave lens will bring the image back to the retina is shown in the given figure.

Fig. 11.1 Myopic eyes and their correction.

Question 3.
What is the far point and near point of the human eye with normal vision?
Far point of the human eye with normal vision is near than infinity and near point is 1.2 m.

Question 4.
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
A student has difficulty reading the black board while sitting in the last row means he is suffering from myopia. This defect can be corrected using concave lens of suitable power.

### MP Board Class 10th Science Chapter 11 NCERT Textbook Exercises

Question 1.
The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to:
(a) presbyopia
(b) accommodation
(c) near-sightednes
(d) far-sightedness
(b) Human eye can change the focal length of the eye lens to see the objects situated at various distances from the eye. This is possible due to the power of accommodation of the eye lens.

Question 2.
The human eye forms the image of an object at its:
(a) cornea
(b) iris
(c) pupil
(d) retina
(d) The human eye forms the image of an object at its retina.

Question 3.
The least distance of distinct vision for a young adult with normal vision is about
(a) 25 m.
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m
(c) 25 cm

Question 4.
The change in focal length of an eye lens is caused by the action of the
(a) pupil.
(b) retina
(c) ciliary muscles
(d) iris
(c) ciliary muscles

Question 5.
A person needs a lens of power – 5.5 dioptres for correcting his distant vision. For correcting his distant vision. For correcting his near vision he needs a lens of power + 1.5 dioptre. What is the focal length of the lens required for correcting (i) distinct vision, and (ii) near vision?
i) Lens required for correcting
distant vision = – 5.5
Focal length of lens F $$=\frac{1}{P}$$
$$\mathrm{F}=\frac{1}{-5.5}=0.181 \mathrm{m}$$
Lens required for correcting this defect =-0.181 M
ii) Lens required for correcting near vision = + 1.5 D
Focal length of lens F $$=\frac{1}{P}$$
$$F=\frac{1}{1.5}=0.667 \mathrm{m}$$

Question 6.
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
The person is suffering from an eye defect called myopia. In this defect, the image is formed in front of the retina. Hence, a concave lens is used to correct this defect of vision.
Object-distance, u = infinity
Image-distance, v = -80 cm
Focal length = f
According to the lens formula,

A concave lens of Power – 1.25 D is required by the person to correct his defect.

Question 7.
Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25 cm.
A person suffering from hypermetropia can see distinct objects clearly but faces difficulty in seeing nearby objects clearly. It happens because . the eye lens focuses the incoming divergent rays beyond the retina. This defect of vision is corrected by using a convex lens. A convex lens of suitable power converges the incoming light in such a way that the image is formed on the retina, as shown in the following figure.

Fig. 11.2: Correction for hypermetropic eye.

The convex lens actually creates a virtual image of a nearby object (N’ in the figure) at the near point of vision (N) of the person suffering from hypermetropia. The given person will be able to clearly see the object kept at 25 cm (Near point of the normal eye), if the image of the object is formed at his near point, which is given as 1 m.

Object-distance, u = -25 cm
Image-distance, v = -1m = -100m
Focal length, f = ?

Using the lens formula,
$$\frac { 1 }{ v }$$ – $$\frac { 1 }{ u }$$ = $$\frac { 1 }{ f }$$
$$\frac { 1 }{ -100 }$$ – $$\frac { 1 }{ -25 }$$ = $$\frac { 1 }{ f }$$
$$\frac { 1 }{ f }$$ = $$\frac { 1 }{ 25 }$$ = $$\frac { 1 }{ f }$$
$$\frac { 1 }{ f }$$ = $$\frac { 1 }{ 25 }$$ – $$\frac { 1 }{ 100 }$$
$$\frac { 1 }{ f }$$ = $$\frac { 4-1 }{ 100 }$$
f = $$\frac { 100 }{ 3 }$$ = 33.3 cm = 0.33cm

A convex lens of power + 3.0 D is required to correct the defect.

Question 8.
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
The maximum accommodation of a normal eye is reached when the object is at a distance of 25 cm from the eye. The focal length of the eye lens cannot be decreased below this minimum limit. Thus an object placed closer than 25cm [or very close to eye] cannot be seen clearly by a normal eye.

Question 9.
What happens to the image distance in the eye when we increase the distance of an object from the eye?
The distance eye lens and retina is the image distance inside the eye. The image distance is fixed. It cannot be changed at all. Therefore, when we increase the distance of an object from the eye, there is no change in the image distance inside the eye.

Question 10.
Why do stars twinkle?
Stars emit their own light and they twinkle due to the atmospheric refraction of light. Stars are very far away from the earth. Hence, they are considered as point sources of light. When the light coming from stars enters the earth’s atmosphere, it gets refracted at different levels because of the variation in the air density at different levels of the atmosphere. When the star’s light refracted by the atmosphere comes more towards us, it appears brighter than when it comes less towards us. Therefore, it appears as if the stars are twinkling at night.

Question 11.
Explain why the planets do not twinkle.
Planets do not twinkle because they appear larger in size than the stars as they are relatively closer to earth. Planets can be considered as a collection of a large number of point-size sources of light. The different parts of these planets produce either brighter or dimmer effect in such a way that the average of brighter and dimmer effect is zero. Hence, the twinkling effects of the planets are nullified and they do not twinkle.

Question 12.
Why does the Sun appear reddish early in the morning?
Light from the Sun near the horizon passes through thicker layers of air and larger distance in the earth’s atmosphere before reaching our eyes. However, light from the Sun overhead would travel relatively shorter distance. At noon, the Sun appears white as only a little of the blue and violet colours are scattered. Near the horizon, most of the blue light and shorter wavelengths are scattered away by the particles. Therefore, the light that reaches our eyes is of longer wavelengths. This gives rise to the reddish appearance of the Sun.

Question 13.
Why does the sky appear dark instead of blue to an astronaut?
When sunlight passes through the atmosphere, the fine particles in air scatter the blue colour (shorter wavelength more strongly than red. The scattered blue light enters our eyes. If the earth had no atmosphere, there would not have been any scattering. Then the sky would have looked dark. The sky appears dark to astronaut flying at very high attitude, as scattering is not prominent at such heights.

### MP Board Class 10th Science Chapter 11 Additional Important Questions

MP Board Class 10th Science Chapter 11 Multiple Choice Questions

Question 1.
When our eye see a near object, its lens?
(a) Expand
(b) Remain same
(c) Contract
(d) None
(a) Expand

Question 2.
What transfer information from eyes to brain?
(a) Neuro trans
(b) Iris
(c) Optical nerve
(d) Retina
(c) Optical nerve

Question 3.
What controls the size of pupil?
(a) Iris
(b) Cornea
(c) Lens
(d) Aqueous humour
(a) Iris

Question 4.
Near point of human eye is approximately:
(a) 50 cm
(b) 1 m
(c) 25 cm
(d) 25 m
(c) 25 cm

Question 5.
Far point of human eye is approximately:
(a) 10 km
(b) infinity
(c) 5 km
(d) 25 cm
(a) 10 km

Question 6.
Cataract is caused mostly to
(a) Farm workers
(b) Factory workers
(c) Kids watching TV and Mobiles
(d) Old age people
(d) Old age people

Question 7.
In which kind of defect, image of a distant object is formed in front of retina?
(a) Myopia
(b) Cataract
(c) Hypermetropia
(d) Presbyopia
(a) Myopia

Question 8.
A concave lens with correct power can help a person with
(a) Hypermetropia
(b) Myopia
(c) Presbyopia
(d) None of these
(b) Myopia

Question 9.
Adjusting “cording to object’s distance from eye is called
(a) Vision power
(b) Motivation
(c) Accommodation power
(d) Presbyopia
(c) Accommodation power

Question 10.
For an eye donation, eyes must be removed within ……… after death.
(a) 8 hours
(b) 25 hours
(c) 4-6 hours
(d) None.
(c) 4-6 hours

Question 11.
What type of lens are required to correct a vision of hypermetropic eyes?
(a) Concave
(b) Convex
(c) both
(d) Plane mirror is required ;
(b) Convex

Question 12.
When we pass a light through a prism, it is
(a) Refracted
(b) Scattered
(c) Reflected
(d) Inverted
(a) Refracted

Question 13.
Which colour lies in centre of a rainbow?
(a) Red
(b) Violet
(c) Yellow
(d) Green
(d) Green

Question 14.
If two prism are placed inverted to each other and white light is passed from one prism, what will we get refracted by other prism?
(a) VIBGYO
(b) white light
(c) All light will be absorbed
(d) Black spot
(b) white light

Question 15.
We see twinkling of stars due to:
(a) Reflection of light.
(b) Refraction of light
(c) Scattering of light
(d) Polarization of light
(b) Refraction of light

Question 16.
Particle looks moving in smoke filled place, when a light beam coming from a whole passes through it, because:
(a) Tyndall effect
(b) atmospheric refraction
(c) White light spectrum
(d) reflection
(a) Tyndall effect

MP Board Class 10th Science Chapter 11 Very Short Answer Type Questions

Question 1.
Where image is formed in our eyes?
Retina.

Question 2.
Which part of eye helps in adjustment of lens according to distance?
Lens.

Question 3.
Which nerve transfer information regarding image to brain?
Optic nerve.

Question 4.
What is power of accommodation?
The ability of the eye to focus both near and distant objects, by adjusting its focal length is called power of accommodation of eyes.

Question 5.
How many points of accommodation are set to observe clarity of a person’s vision?
Two-far point and near point.

Question 6.
What is the maximum distance till which a person with normal eye can see?
No limit, infinite distance.

Question 7.
Name common refractive defects of eyes.
Myopia, Hypermetropia and Presbyopia.

Question 8.
What kind of lens is used to correct a myopic defect in a person?
Concave.

Question 9.
What kind of treatment is available to correct a cataract?
Surgery.

Question 10.
What is bifocal lens?
Lens made by both concave and convex lens is called bifocal lens.

Question 11.
What happens to the light ray entering a prism?
The light ray get refracted.

Question 12.
What happens if white light is passed through a prism?
It Scatters to seven colours spectral pattern.

Question 13.
What is an emergent ray?
Ray which comes out after being refracted from a prism is called emergent ray.

Question 14.
Why sky looks red at sunrise and sunset?
Scattering of white light.

Question 15.
Which colour light bend most after coming out of a triangular prism?
Violet.

Question 16.
Why we never see a shadow without light?
When light passes through an object, it get partially deviated or absorbed so, disappear from that very way which forms a shadow.

Question 17.
Why light ray in a dusty room look sparkling and moving?
Due to tyndall effect.

Question 18.
Why we can observe a star twinkling?
Due to atmospheric refraction.

Question 19.
What is the time difference between actual and observed sunrise and sunset?
2 minutes.

Question 20.
Why sky looks blue to all of us?
Due to scattering of light.

MP Board Class 10th Science Chapter 11 Short Answer Type Questions

Question 1.
Why does the Sun appear reddish early in the morning?
Early in the morning, the sun is near the horzion. Sunlight reaches us after covering a large thickness of the atmosphere. So, shorter waves of blue region are almost completely scattered away by the air molecules. Red waves of longer wavelength are least scattered and reach our eyes. The sun appears red.

Question 2.
Why does the sky appear dark instead of blue to an astronaut?
The atmosphere is quite thin at very high altitudes. There is almost no scattering of sunlight. So, the sky appears dark to an astronaut.

Question 3.
Why is a concave lens used to correct myopia or short-sightedness?
A concave lens of suitable focal length diverges the parallel rays from the distant object as if they are coming from the far point F of the myopic eye. This helps the eye lens to form a clear image at the retina.

Question 4.
Dispersion is caused by refraction not by reflection. Why?
The reason is that for a given angle of incidence, the angle of reflection is same for all the wavelengths of white light while the angle of refraction is different for different wavelengths.

Question 5.
A hypermetropic person prefers to remove his spectacles, while driving. Give reason.
When a hypermetropic person wearing the spectacles looks at a distant object, the parallel rays from the distant object get converged in front of the retina. The image appears blurred. In order to avoid this, the person prefers to remove his spectacles.

Question 6.
Give reasons for the following:

1. The stars appear to twinkie.
2. The planets do not twinkle.

1. Stars appear to twinkle due to atmospheric refraction of starlight and physical conditions of the earth’s atmosphere are not being stationary.
2. Planets are much closer to the earth and are seen as extended sources. The fluctuations caused in the amount of light due to atmospheric refraction are negligible. Hence, planets do not twinkle.

MP Board Class 10th Science Chapter 11 Long Answer Type Questions

Question 1.
Why does the Sun seem to rise two minutes before the actual sunrise and set two minutes after the actual sunset? Explain with the help of labelled diagram.
Advance sunrise and delayed sunset. Apparent shift in the position of sun at sunrise and sunset:
The sun is visible before actual sunrise and after actual sunset, because of atmospheric refraction. With altitude, the density and hence, refractive index of air-layer decreases. As shown in Fig. given the light rays starting from the sun travel from rarer to denser layers. They bend more and more towards the normal. To an observer on the earth, light rays appear to come from position S. The sun which is actually in position S below the horizon appears in position S above the horizon.

Fig. 11.6: Atmospheric refraction effect at sun rise.

Thus, the sun appears to rise early by about two minutes and for the same reason, it appears to set late by about two minutes. This increases the length of the day by about four minutes.

Question 2.
“Stars appear higher than they actually are.” Give reason.
Or
Is the position of a star as seen by us its true position? Justify your answer.
Since, the atmosphere bends starlight towards the normal, the apparent position of the star is slightly different from its actual position. The stars appear slightly higher (above) than their actual position when viewed near the horizon.

Question 3.
Why do we observe the apparent random wavering or flickering of objects when seen through a turbulent stream of hot air rising above fire, a stove or radiator?
This is due to atmospheric refraction i.e., refraction of light by the earth’s atmosphere. The air just above the fire becomes hotter than air further up. Hotter air is lighter (less denser) than the cooler air (denser) above it. This causes refraction of light due to decrease of refractive index with decreasing density or increasing temperature. Since, the physical conditions of the refracting medium (air) are not stationary, the apparent positions of the objects, as seen through the hot air, fluctuate. Consequently, the objects seen through such air show a wavering effect.

Question 4.
Why do we see stars appear twinkling whereas planets do not twinkle?
Or
A star sometimes appear brighter and some other times fainter. What is this defect called, state reason for this effect.
Twinkling of stars: Differential the apparent position of a star is slightly different from the actual position due to refraction of starlight by the atmosphere. Further, this apparent position is not stationary but keeps on changing due to the change in atmospheric conditions like density, temperature etc. The path of the rays of light coming from the star goes on varying slightly. The amount of light entering our eyes from a particular star increases or decreases randomly with time.

Fig. 11.7: Apparent star position due to atmospheric refraction.

Sometimes, the star appears bright and other times, it appears fainter. This gives rise to the twinkling effect of the star.

The planets do not show twinkling effect. As the planets are much closer to the earth, the amount of light received from them is much greater and the fluctuations caused in the amount of light due to atmospheric refraction are negligible as compared to the amount of light received from them.

Question 5.
What is tyndall effect? What is its cause? Name two phenomena observed in daily life which are based on Tyndall effect.
Or
A beam of light is allowed to pass through two beakers A and B containing a true solution and colloidal solution respectively. What do you observe? Name the phenomenon responsible for your observation.
Tyndall effect: When a beam of light is passed through a colloidal solution, placed in a dark room, the path of beam becomes illuminated (or visible), when observed through a microscope placed perpendicular to the path of light. This effect is called Tyndall effect.

On the other hand, the path of a beam of light is not visible through a true solution, as shown in figure 11.8.

Fig. 11.8: Tyndall effect.

Cause of Tyndall effect: The size of the colloidal particle is relatively larger than the solute particle of a true solution. The colloidal particles first absorb energy from the incident light and then scatter a part of this energy from their surfaces. Thus, Tyndall effect is due to scattering of light by the colloidal particles and the colloidal particles are seen as points of light moving against a dark background.

Some daily life phenomena based on Tyndall effect are as follows:

1. When a fine beam of sunlight enters a smoke filled room through a small hole, the smoke particles become visible due to the scattering of light.
2. When sunlight passes through a canopy of a dense forest, the tiny water droplets in the mist scatter light and become visible.

### MP Board Class 10th Science Chapter 11 NCERT Textbook Activities

Class 10 Science Activity 11.1 Page No. 192

• Fix a sheet cf white paper on a drawing board using drawing pins.
• Fife a glass prism on it in such a way that it rests on its triangular fee. Trace the outline of the prism using a pencil.
• Draw a straight line PE inclined to one of the refracting surfaces, say AB, of the prism.
• Fix two pins, say at points P and Q, on the line PE as shown in Fig. 11.3.
• Look for the images of the pins, fixed at P and Q, through the other face AC.
• Fix two more pins, at points R and S, such that the pins at R and S and the images of the pins at P and Q lie on the same straight line.
• Remove the pins and the glass prism.
• The line PE meets the boundary of the prism at point E (see Fig. 11.3). Similarly, join and produce the points R and S. Let these lines meet the boundary of the prism at E and F, respectively. Join E and F.
• Draw perpendiculars to the refracting surfaces AB and AC of the prism at points E and F, respectively.
• Mark the angle of incidence (∠i), the angle of refraction (∠r) and the angle of emergence (∠e) as shown in Fig. 11.3.

PE – Incident ray – ∠i – Angle of incidence
EF – Refracted ray ∠r – Angle of refraction
FS – Emergent ray ∠e – Angle of emergence
∠A – Angle of the prism – ∠D – Angle of deviation

Fig. 11.3 : Refraction of tight through a triangular glass prism

Observations:

• The light rays enter the prism and emerge out as the emergent ray. The light ray bent towards the normal upon refraction. At the second surface, the light ray enters from glass to air. The emergent ray appears to be coming along the rays FRS, the angle between the incident ray produced forward and the emergent ray produced backward, is called the angle of deviation.

Class 10 Science Activity 11.2 Page No. 193

• Take a thick sheet of cardboard and make a small hole or narrow slit in its middle.
• Allow sunlight to fall on the narrow slit. This gives a narrow beam of white light.
• Now, take a glass prism and allow the light from the slit to fall on one of its faces as shown in Fig. 11.4.

Fig. 11.4: Dispersion of white light by the glass prism.
• Turn the prism slowly until the light that comes out of it appears on a nearby screen.
• What do you observe? You will find a beautiful band of colours. Why does this happen?

Observations:

• The white light gets dispersed into seven colour components by a prism. The band of the coloured components of a light beam is called spectrum. The splitting of light into its component colours is called dispersion. The colours bends at different angles as they pass through prism and are observed separately as VIBGYOR.

Class 10 Science Activity 11.3 Page No. 196

• Place a strong source (S) of white light at the focus of a converging lens (L). This lens provides a parallel beam of light.
• Allow the light beam to pass through a transparent glass tank containing clear water.
• Allow the beam of light to pass through a circular hole (e) made in a cardboard. Obtain a shaip image of the circulai hole on a screen (MN) using a second converging lens (L2), as shown in Fig. 11.5

Fig. 11.5: An arrangement for observing scattering of light in colloidal solution.
• Dissolve about 200 g of sodium thiosulphate (hypo) in about 2 L of clean water taken in the tank. Add about 1 to 2 mL of concentrated sulphuric acid to the water. What do you observe?

Observations:

• The microscopic particles of sulphur precipitate, in about 2 to 3 minutes. As they precipitate, the blue light from the three sides of the glass tank is seen. This happens due to scattering of short wavelengths by minute colloidal sulphur particles.

## MP Board Class 10th Science Solutions Chapter 4 Carbon and Its Compounds

### MP Board Class 10th Science Chapter 4 Intext Questions

Intext Questions Page No. 61

Question 1.
What would be the electron dot structure of carbon dioxide which has the formula CO2?

Question 2.
What would be the electron dot structure of a molecule of sulphur which is made up of eight atoms of sulphur? (Hint: The eight atoms of sulphur are joined together in the form of a ring).

Intext Questions Page No. 68,69

Question 1.
How many structural isomers can you draw for pentane?
Three structural isomers are possible for pentane.

Question 2.
What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
The two features of carbon that give rise to a large number of compounds are as follows:

1. Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called catenation.
2. Since carbon has a valency of four, it is capable of bonding with four other atoms of carbon or atoms of some other mono-valent element.

Question 3.
What will be the formula and electron dot structure of cyclopentane?
The formula for cyclopentane is C5H10. Its electron dot structure is given below:

Question 4.
Draw the structures for the following compounds:
(i) Ethanoic acid
(ii) Bromopentane
(iii) Butanone
(iv) Hexanal
Are structural isomers possible for bromo-pentane?

Yes, there are many structural isomers possible for bromo-pentane. Among them, the structures of the three isomers are given.

Question 5.
How would you name the following compounds?

(i) Bromoethane
(ii) Methanal (formaldehyde)
(iii) Hexyne.

Intext Questions Page No. 71

Question 1.
Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Addition reaction means adding oxygen. Adding ethanol to potassium permanganate, we get ethanoic acid. Hence this reaction is called oxidation reaction.

Since in this reaction one oxygen is added to ethanol, hence it is an oxidation reaction.

Question 2.
A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
If a mixture of oxygen and ethyne is burnt, then ethyne burns completely producing a blue flame. The oxygen ethyne flame is extremely hot and produces a very high temperature which is used for welding metals. A mixture of ethyne and air is not used for welding because the burning of ethyne in air produces a sooty flame due to incomplete combination which is not enough to melt metals for welding.

Intext Questions Page No. 74

Question 1.
How would you distinguish experimentally between an alcohol and a carboxylic acid?

1. We can distinguish between an alcohol and a carboxylic acid on the basis of their reaction with carbonates and hydrogen carbonates. The acid reacts with carbonate and hydrogen carbonate to evolve CO2 gas that turns lime-water milky.
2. Metal carbonate/Metal hydrogen carbonate + Carboxylic acid → Salt + Water + Carbon dioxide.
3. In the litmus test, alcohol shows no change in colour whereas carboxylic acid turns blue litmus red.
With sodium metal, alcohol gives effervescence but carboxylic acid does not give it. Alcohols, on the other hand, do not react with carbonates and hydrogen carbonates.

Question 2.
What are oxidising agents?
some substances are capable of adding oxygen to others. These substances are known as oxidising agents.

Intext Questions Page No. 76

Question 1.
Would you be able to check if the water is hard by using a detergent?
Margents are remaining effective in hardwater. Because of this reason, we can check if water is hard by using a detergent.

Question 2.
People use a variety of methods to wash clothes. Usually after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?
The soap molecules form structures called micelles in water, where one end of the molecules is towards the oil droplet while the ionic end-faces outside. This forms emulsion in water and we can wash our clothes clean.

### MP Board Class 10th Science Chapter 4 Ncert Textbook Exercises

Question 1.
Ethane, with the molecular formula C2H6 has –
(a) 6 covalent bonds
(b) 7 covalent bonds
(c) 8 covalent bonds
(d) 9 covalent bonds
(b) 7 covalent bonds.

Question 2.
Butanone is a four-carbon compound with the functional group.
(a) Carboxylic acid
(b) Aldehyde
(c) Ketone
(d) Alcohol
(c) Ketone.

Question 3.
While cooking, if the bottom of the vessel is getting blackened on the outside, it means that.
(a) The food is not cooked completely.
(b) The fuel is not burning completely.
(c) The fuel is wet.
(d) The fuel is burning.
(b) the fuel is not burning completely

Question 4.
Explain the nature of the covalent bond using the bond formation in CH3Cl.
The structure of CH3Cl is given below:

Carbon has four valence electrons. It shares one electron each with three hydrogen atoms and one electron with chlorine. The bond between C and Cl atoms is covalent but due to higher value of electro-negativity of Cl, the C-Cl bond is polar in nature.

Question 5.
Draw the electron dot structures for:
(a) Ethanoic acid
(b) H2S
(c) Propanone
(d) F2

Question 6.
What is a homologous series? Explain with an example?
A series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series.
Eg: CH4 and C2H6 – These differ by a CH2 unit.
C2H6 and C3H8 – these differ by a CH2 unit.

Question 7.
How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Ethanol and Ethanoic acid can be differentiated on the basis of their following properties by:

1. Ethanol is a liquid at room temperature with a pleasant smell. Ethanoic acid has a melting point of 17°C. Since it is below the room temperature so, it freezes during winter. Moreover, ethanoic acid has a smell like vinegar.
2. Ethanol does not react with metal carbonates while, ethanoic acid reacts with metal carbonates to form a salt, water and carbon dioxide.
For example:
2CH3COOH + Na2CO3 → 2CH3COONa + CO2 +H2O
3. Ethanol does not react with NaOH while ethanoic acid reacts with NaOH to form sodium ethanoate and water.
For example,
CH3COOH + NaOH → CH3COONa + H2O
4. Ethanol is oxidized to give ethanoic acid in the presence of acidified KMnO4 while no reaction takes place with ethanoic acid in the presence of acidified KMnO4.

Difference in physical properties:

 Ethanol Ethanoic acid This is in liquid form at room temperature. Its melting point is 156° K. Its melting point is 290K and hence it often freezes during winter in cold climates. Difference in chemical properties Ethanol will not react with metallic carbo­nates. Ethanoic acid reacts with carbo­nates and Hydrogen carbonate and forms salts, carbon dioxide and water.

Question 8.
Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Soaps are molecules in which the two ends have differing properties, one is hydrophilic that is, it interacts with water, while the other end is hydrophobic, that is it interacts with hydrocarbons. When soap is at the surface of water, the hydrophobic tail of soap will not be soluble in water and the soap will align along the surface of water with the ionic end in water and the hydrocarbon tail protruding out of water. Thus, clusters of molecules in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. This formation is called a micelle. Soap in the form of a micelle is able to clean. A micelle will not be formed in other solvents such as ethanol.

Question 9.
Why are carbon and its compounds used as fuels for most applications?
Carbon and its compounds give large amount of heat on combustion due to the high percentage of carbon and hydrogen. Carbon compounds used as fuel have optimum ignition temperature with high calorific values and are easy to handle. Their combustion can be controlled. Therefore, carbon and its compounds are used as fuels.

Question 10.
Explain the formation of scum when hard water is treated with soap.
When soap reacts with water, calcium and magnesium salts are formed which causes hardness for water. Ionic ends of soap interacts with water while the carbon chain interacts with oil. The soap molecules, thus form structures called micelles where one end of the molecules is towards the oil droplet while the ionic-end faces outside. This forms an emulsion in water.

Question 11.
What change will you observe if you test soap with litmus paper (red and blue)?
Since soap is basic in nature, it will turn red litmus blue. However, the colour of the blue litmus will remain blue.

Question 12.
What is hydrogenation? What is its industrial application?
Unsaturated Hydrocarbons react with Hydrogen, in presence of catalysts such as palledium or Nickel and forms saturated Hydrocarbons. This is called Hydrogenation of oils.
This process is useful in hydrogenation of oils derived from plants.

Question 13.
Which of the following hydrocarbons undergo addition reactions:
C2H6, C3H8, C3H6, C2H2 and CH4.
Unsaturated hydrocarbons undergo addition reactions. Being unsaturated hydrocarbons, C3H6 and C2H2 undergo addition reactions.

Question 14.
Give a test that can be used to differentiate between saturated and unsaturated hydrocarbons.
Saturated Hydrocarbons will not react with Bromine, but unsaturated hydrocarbons change the colour of Bromine.

Question 15.
Explain the mechanism of the cleaning action of soaps.
The dirt present on clothes is organic in nature and insoluble in water. Therefore, it cannot be removed by washing with water only. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in the water. Hence, the dust particles are easily rinsed away by water.

### MP Board Class 10th Science Chapter 4 Additional Questions

MP Board Class 10th Science Chapter 4 Multiple Choice Questions

Question 1.
Which of the following is a three-carbon compound?
(a) Ethene
(b) Ethane
(c) Propane
(d) Acetylene
(c) Propane

Question 2.
Which one of the following is an unsaturated hydrocarbon?
(a) Acetylene
(b) Butane
(c) Propane
(d) Decane
(a) Acetylene

Question 3.
Two neighbours of homologous series differ by:
(a) -CH
(b) -CH2
(c) -CH3
(d) -CH4
(b) -CH2

Question 4.
General formula of alkanes is –
(a) CnH2n+2
(b) CnH2n
(c) CnH2n-2
(d) CnHn
(a) CnH2n+2

Question 5.
Which of the following represents alkynes?
(a) -C – C-
(b) -C = C-
(c) -C ≡ C-
(d) None of these
(c) -C ≡ C-

Question 6.
Which of the following represents ketones?
(a) -C = O
(b) -OH
(c) -CHO
(d) COOH
(a) -C = O

Question 7.
Which of the following is not an aliphatic hydrocarbon?
(a) ethene
(b) ethane
(c) propyne
(d) benzene
(d) benzene

Question 8.
Complete combustion of a hydrocarbon gives:
(a) CO + H2O
(b) CO2 + H2O
(c) CO + H2
(d) CO2 + H2
(b) CO2 + H2O

Question 9.
Which is NOT correct for isomers of a compound?
(a) They differ in physical properties.
(b) They differ in chemical properties.
(c) They have the same molecular formula.
(d) They have the same structural formula.
(d) They have the same structural formula.

Question 10.
Buckminsterfullerene is an example of ………….. of carbon.
(a) an isomer
(b) an isotope
(c) an allotrope
(d) a functional group
(c) an allotrope

Question 11.
Who prepared urea for the first time by heating ammonium cyanate?
(a) Wohler
(b) Lavoisier
(c) Fuller
(d) Haber
(a) Wohler

Question 12.
Hexanone is a four-carbon compound with the functional group:
(a) Carboxylic acid
(b) Aldehyde
(c) Ketone
(d) Alcohol
(c) Ketone

Question 13.
Major constituent of LPG is ………….
(a) Ethene
(b) Butane
(c) Propane
(d) Pentane
(b) Butane

Question 14.
The gas used in welding and cutting metals is:
(a) Ethyne
(b) Ethene
(c) Ethane
(d) Propane
(a) Ethyne

Question 15.
How is carbon atoms arranged in Buckminster fullerenes?
(a) Triangle shape
(b) Hexagonal array
(c) Football shape
(d) None
(c) Football shape

Question 16.
Vinegar is a solution of –
(a) 40%-45% acetic acid.
(b) 90%-95% acetic acid.
(c) 5-20% acetic acid and water.
(d) 35-40% acetic acid and water.
(c) 5-20% acetic acid and water.

Question 17.
How many covalent bonds are there in Bromoethane?
(a) 4
(b) 6
(c) 10
(d) 7
(d) 7

Question 18.
Which functional group is present in propane?
(a) Aldehyde
(b) No group
(c) Ketone
(d) Alcohol
(b) No group

Question 19.
Which compound/molecule is being presented by the following formula: H: C:: C: H
(a) Ethane
(b) Ethene
(c) Ethyne
(d) None of these
(b) Ethene

Question 20.
Next homologous to C2H5OH will be:
(a) CH4
(b) C2H6
(c) C3H5
(d) C3H7OH
(d) C3H7OH

Question 21.
When we burn naphthalene it produces:
(a) Smoky flame
(b) Non-sooty flame
(c) Colourless flame
(d) No flame
(a) Smoky flame

Question 22.
Bunsen burner is used for:
(a) making food.
(b) study flames type.
(c) low heating work.
(d) all the above.
(c) low heating work.

Question 23.
See the figure carefully.

Choose the suitable name of isomer:
(a) Neo-pentane
(b) n-pentane
(c) Iso-pentane
(d) All
(c) Iso-pentane

Question 24.
Which of the following is a structure of ethanoic acid?

Question 25.
What is the name of CH3-CH2-Br? Choose from the following:
(a) Hex-1-one
(b) Hexanal
(c) Ethanoic acid
(d) None
(d) None

Question 26.
What happens on the litmus test of soap?
(a) No change
(b) Red litmus turns blue
(c) Red litmus turn purple
(d) Red litmus turn green
(b) Red litmus turns blue

MP Board Class 10th Science Chapter 4 Very Short Answer Type Questions

Question 1.
Name two groups which can have the same general formula.
Both alkenes and cyclo-alkanes can be represented by the same general formula.

Question 2.
Which group of compounds have general formula C2H2n?
The general formula CnH2n represents alkenes group of compounds.

Question 3.
What is the common name and IUPAC name for CH3COCH3?
Acetone is the common name and propanone is the IUPAC name for CH3COCH3.

Question 4.
Do isomers always show same chemical properties?
No, isomers always do not show the same chemical properties.

Question 5.
What is the common name and formula for ethanol?
Alcohol, CH3CH2OH.

Question 6.
What are the products of complete combustion of a hydrocarbon?
Carbon dioxide and water.

Question 7.
What is next homologue of C3H7OH is called?
The next homologue of C3H7OH is called butanol C4H9OH.

Question 8.
What are isomers?
The compounds which have the same molecular formula but different structures and chemical properties are called isomers.

Question 9.
Which one are more reactive unsaturated hydrocarbons or saturated hydrocarbons? Give reason.
Unsaturated hydrocarbons: The Presence of double and triple covalent bonds make them more reactive.

Question 10.
Discuss the general nature of covalent compounds in water.
Generally, they are insoluble in water.

Question 11.
What type of hydrocarbons takes part in an addition reaction?
Unsaturated hydrocarbons.

Question 12.
Which carboxylic acid freezes during winter or under cold climate conditions?
Acetic acid and hence, known as glacial acetic acid.

Question 13.
What is the difference in molecular masses of any two successive homologous alkanes?
14 units.

Question 14.
What is the molecular formula of the alcohol which can be derived from propane?
Alcohol obtained from propane is propanol -1 and the molecular formula is C3H7OH.

Question 15.
Give the names of the functional groups: (CBSE 2007)

1. -CHO
2. -COOH

1. Aldehydic group.
2. Carboxylic acid group.

Question 16.
Give the names of the following functional groups: (CBSE 2007)

1. -OH
2. -CO

1. Alcoholic.
2. Ketonic.

MP Board Class 10th Science Chapter 4 Short Answer Type Questions

Question 1.
What is meant by the term functional group?
An atom or a group of atoms, which makes a carbon compound reactive and decides its properties, is called a functional group.
For example aldehyde, ketone etc.

Question 2.
Which R functional groups always occur at the terminal position of a carbon chain?
Aldehydic Group, R-CHO (R is the alkyl group),
Carboxyl Group, R-COOH (R is the alkyl group)

Question 3.
Why a candle flame burns yellow, while a highly-oxygenated gas fuel flame burns blue?
The most important factor determining the colour of the flame is oxygen supply and the extent of fuel-oxygen, which determines the rate of combustion and thus, the temperature and reaction paths, thereby producing different colour hues. In case of a candle, it is incomplete combustion and the flame temperature is not high. This gives a yellow flame, while a highly-oxygenated gas (e.g., ethyne) flame burns blue because of complete combustion raising a very high temperature.

Question 4.
Why is the reaction between methane and chlorine considered a substitution reaction? (CBSE 2008)
Methane reacts with chlorine in the presence of sunlight to form chloromethane and hydrogen chloride. Since chlorine substitutes or replaces hydrogen of methane to form chloromethane, it is considered as substitution reaction.
CH4 + Cl2 → CH3Cl + HCl
With the excess of chlorine, four hydrogen atoms of methane are replaced by chlorine atoms to form carbon tetrachloride (CCl4).

Question 5.
Why does carbon form compounds mainly by covalent bonding?
Being tetravalent carbon atom, it is neither capable of losing all of its four valence electrons nor it can easily accept four electrons to complete its octet. Both of these are requirements of ionic bond formation and are energetically less favourable. Carbon completes its octet by sharing electrons and hence, covalent bonding is preferred.

Question 6.
What do you mean by Octane rating?
Gasoline is rated on a scale known as octane rating, which is based on the way they burn in an engine. The higher the octane rating, the greater the percentage of complex-structured hydrocarbons that are present in the mixture, the more uniformly the gasoline burns, and the less knocking there is in the automobile engine. Thus, a gasoline rated 92 octane will burn more smoothly than one rated 87 octanes.

Question 7.
What is covalent bonding?
The chemical bonding that takes place due to the mutual sharing of electron pairs of two or more atoms of different elements is called covalent bonding. By mutual sharing of electron pairs, atom attains noble gas configuration, e.g., hydrogen molecule (H2), the two H-atoms combine by covalent bonding (H-H).

Question 8.
What are hydrocarbons? Give examples.
Compounds of carbon and hydrogen are called hydrocarbons. Methane, ethane, butane, ethyne, propane, benzene, petroleum products – all are examples of hydrocarbons.

Question 9.
What are saturated hydrocarbons? (CBSE 2011)
The hydrocarbons in which valency of carbon is satisfied by a single covalent bond are called saturated hydrocarbons. Alkanes like methane (CH4), ethane(C2H6), propane (C3H8) etc. are examples of saturated hydrocarbons. Saturated hydrocarbons will generally give a clean flame.

Question 10.
Why do ionic compounds have high melting points? (HOTS)
Ions have strong electrostatic forces of attraction among them forming ionic compounds. It requires a lot of energy to break these ionic bonds or forces. That’s why ionic bonds have high melting points.

Question 11.
What are homologous series? (HOTS)
Homologous series are:

1. Compounds with the same formula.
2. Belong to the same functional group.
3. Have general methods of separation.
4. Have similar chemical properties.

Show similar gradation of physical properties, e.g., boiling points of alcohol increase with an increase in their molecular weights. Similarly, solubility decreases with increase in molecular weights.

Question 12.
What is a heteroatom? What is the heteroatom in the alcohol functional group? (HOTS)
In a hydrocarbon chain, one or more hydrogen atoms can be replaced by other atoms according to their valencies. The element wh replaces hydrogen in the chain is called a heteroatom, e.g., in alcohol (-OH) functional group, oxygen is the heteroatom.

MP Board Class 10th Science Chapter 4 Long Answer Type Questions

Question 1.
Distinguish between saturated and unsaturated hydrocarbons by the way of their burning in air and bromine test inferences.
1. Saturated compounds are burnt in air, to give a clear (blue) flame but the burning of unsaturated compounds (alkenes and alkynes) give a sooty (yellowish) flame because saturated compounds contain comparatively less percentage of carbon which is completely oxidized by the oxygen present in the air.

On the other hand, the percentage of carbon in unsaturated compounds is more and it requires more oxygen to get completely oxidized that is not fulfilled by air. So, due to incomplete oxidation, they burn with a sooty flame.

2. Bromine-water test: Br2 water is a brown coloured liquid:

1. Unsaturated hydrocarbons give addition reaction with Br2. So, the colour of Br2 water gets decolourised.
2. Saturated hydrocarbons do not react with Br2 water, so the colour of B2-water does not get decolourised.

Question 2.
Two compounds A and B react with each other in the presence of a dehydrating agent to produce an ester. Both react with Na to evolve hydrogen gas. On reaction with Na2CO3, only A evolves CO2. Identify the functional groups present in A and B giving the reason for your answer.
Compound A contains -COOH group while compound B contains -OH group. Since, carboxylic acids and alcohols react with each other to form an ester, out of A and B, one is an alcohol and the other is a carboxylic acid. This is further strengthened by the reaction of both with Na to evolve hydrogen gas. Only carboxylic acids react with Na2CO3 to evolve CO2, A contains -COOH group while B contains -OH group.

Question 3.
An organic compound ‘X’ is widely used as a preservative in pickles and has a molecular formula C2H2O2. This compound reacts with ethanol to form a sweet-smelling compound ‘Y’.

1. Identify the compound ‘X’.
2. Write the chemical equation for its reaction with ethanol to form compound ‘Y’.
3. How can we get compound ‘X’ back from ‘Y’?
4. Name the process and write a corresponding chemical equation.
5. Which gas is produced when compound ‘X’ reacts with washing soda? Write the chemical equation.
7. Compound X is ethanoic acid which gives and ester (Y) when reacts with ethanol.
8. CH3COOH + CH3CH2OH → CH3COOC2H5.
9. Esters give back alcohol and carboxylic acid in the presence of acid or base.
10. Saponification reaction: CH3COOC2H5 + NaOH → C2H5OH + CH3COOH + Na.
11. CO2 gas is released,
CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2.

Question 4.
“Saturated hydrocarbons burn with a blue flame while unsaturated hydrocarbons burn with a sooty flame.” Why?
Saturated hydrocarbons have only C-C and C-H single bonds and thus, contain the maximum possible number of hydrogen atoms per carbon atom. With sufficient oxygen, saturated hydrocarbons burn completely and give blue flame,
CH4 + 2O2 → CO2 + 2H2O
Unsaturated hydrocarbons contain a carbon-carbon double bond (C=C) or triple bond (C=C). Hence, they contain less number of hydrogen than carbon. Unsaturated hydrocarbons undergo incomplete combustion and give yellow flame along with black sooty carbon.
C2H4 + O2 → CO2 + 2H2O + C(s)

Question 5.
What makes some molecular formula compound different? (HOTS)
The arrangement makes them different compounds with identical molecular formula but different structures are called structural isomers. Organic compounds show a great level of isomerism. Isomers may be structural (due to difference in the arrangement of C atoms forming chain) or stereo (due to arrangement of bonds in a chain). With the increase in the number of carbon atoms in molecular formula, it leads to an increase in the number of isomers.
For example:

### MP Board Class 10th Science Chapter 4 Textbook Activities

Class 10 Science Activity 4.1 Page No. 58

1. Make a list of ten things you have used or consumed since the morning.
2. Compile this list with the lists made by your classmates and then sort the items into the following table.
3. If there are items which are made up of more than one material, put them into both the relevant columns.
4. (C) Indicates carbon. Most substances contain carbon in it.

Class 10 Science Activity 4.2 Page No. 67

1. Calculate the difference in the formulae and molecular masses for
(a) CH3OH and C2H5OH.
(b) C2H5OH and C3H7OH.
(c) C3H7OH and C4H9OH.
2. Is there any similarity between these three?
3. Arrange these alcohols in the order of increasing carbon atoms to get a family. Can we call this family a homologous series?
4. Generate the homologous series for compounds containing up to four. carbons for the other functional groups given in the above table.

Difference: 70 – 60 = 14U
All three groups given above are homologous.

Class 10 Science Activity 4.3 Page No. 69

Caution:

1. This Activity needs the teacher’s assistance.
2. Take some carbon compounds (naphthalene, camphor, alcohol) one by one on a spatula and burn them.
3. Observe the nature of the flame and note whether smoke is produced.
4. Place a metal plate above the flame. Is there a deposition on the plate in case of any of the compounds?

Observations:

Class 10 Science Activity 4.4 Page No. 69

1. Light a bunsen burner and adjust the air hole at the base to get different types of flames/presence of smoke.
2. When do you get a yellow, sooty flame?
3. When do you get a blue flame?

Observations:

1. Yellow, Sooty flame is formed – when the hole is closed.
2. A blue flame is observed – when the hole is open.

Class 10 Science Activity 4.5 Page No. 70

1. Take about 3 ml of ethanol in a test tube and warm it gently in a water bath.
2. Add a 5% solution of alkaline potassium permanganate drop by drop to this solution.
3. Does the colour of potassium permanganate persist when it is added initially?
4. Why does the colour of potassium permanganate not disappear when excess is added?

Observations:
Doing the above activities we found that potassium permanganate act here as oxidising agents only and their colour do not change at,

Class 10 Science Activity 4.6 Page No. 72

Teacher’s demonstration:

1. Drop a small piece of sodium, about the size of a couple of grains of rice, into ethanol (absolute alcohol).
2. What do you observe?
3. How will you test the gas evolved?

Observations:
Sodium is an inflammable substance hence, it should be handled very carefully. When we place it in alcohol, hydrogen gas is evolved and sodium ethoxide is formed,
2Na + 2CH3CH2OH → 2CH3CH2ONa+ + H2

Class 10 Science Activity 4.7 Page No. 73

1. Compare the pH of dilute acetic acid and dilute hydrochloric acid using both litmus paper and universal indicator.
2. Are both acids indicated by the litmus test?
3. Does the universal indicator show them as equally strong acids?

Observations:
The litmus test and pH test show the acidity and alkalinity of substance or chemical:

Class 10 Science Activity 4.8 Page No. 73

1. Take 1 ml ethanol (absolute alcohol) and 1 ml glacial acetic acid along with a few drops of concentrated sulphuric acid in a test tube.
2. Warm in a water-bath for at least five inutes as shown in Figure.
3. Pour into a beaker containing 20-50 ml of water and smell the resulting mixture.

Observations:
When acetic acid reacts with alcohol a new compound with an ester functional group is formed. It has fruit like smell. This reaction is called esterification reaction.

Class 10 Science Activity 4.9 Page No. 74

1. Take a spatula full of sodium carbonate in a test tube and add 2 ml of dilute ethanoic acid.
2. What do you observe?
3. Pass the gas produced through freshly prepared lime-water. What do you observe?
4. Can the gas produced by the reaction between ethanoic acid and carbonate be identified by this test?
5. Repeat this Activity with sodium hydrogen carbonate instead of sodium carbonate.

Observations:
Sodium acetate is produced when we add carbonate or hydrogen carbonate to acetic acid.
2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2

Class 10 Science Activity 4.10 Page No. 74

1. Take about 10 mL of water each in two test tubes.
2. Add a drop of oil (cooking oil) 10 both the test tubes and table them as A and B.
3. To test tube B add a few drops of soap solution.
4. Now shake both the test tubes vigorously for the same period of time.
5. Can you see the oil and water layers separately in both the test tubes immediately after you stop shaking them?
6. Leave the test tubes undisturbed for some time and observe. Does the oil layer separate out? In which test tube does this happen first?

Observations:
Yes, a layer of oil separates out by reacting with the soap solution. Dirt has an oily nature. It happens first in test tube B.

MP Board Class 10th Science Solutions

## MP Board Class 10th Science Solutions Chapter 9 Heredity and Evolution

### MP Board Class 10th Science Chapter 9 Intext Questions

Class 10th Science Chapter 9 Intext Questions Page No.143

Question 1.
If a trait Aexists in 10% of a population of an asexually reproducing species and trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Trait ‘B’ is likely to have arisen earlier. Because in asexually reproducing species, small differences are seen due to DNA replication.

Question 2.
How does the creation of variations in a species promote survival?
Depending on the nature of variations, different individuals would have different kinds of advantages. Bacteria that can withstand heat will better in a heat wave, as selection of variants by environmental factors forms the basis for evolutionary process.

Class 10th Science Chapter 9 Intext Questions Page No. 147

Question 1.
How do Mendel’s experiments show that traits may be dominant or recessive?
Mendel used a number 0 contrasting visible characters of garden peas-round/wrinkled seeds, tall/short plants, white/violet flowers and so on. He took pea plants with different characteristics a tall plant and a shot plant, produced progeny by crossing then, and calculated the percentages of tall or short progeny.

In the first place, there were no halfway characteristics in this first generation, or F1 progeny no medium-height plants. All plants were tall. This means that only one of the parental traits was seen, not some mixture of the two, so the next question was were the tall plants in the F1 generation exactly the same as the tall plants of the parent generation? Mendelian experiments test this by getting both the parental plans and these F1 tall plants to reproduce by self-pollination.

The progeny of the parental plants are of course, all tall. However the second generation, or F2 progeny of the F1 tall plants are not all tall. Instead, one quarter of them are short. This indicates that both the tallness and shortness traits were inherited in the F1 plants, but only the tallness trait was expressed. This led Mendel to propose that two copies of factor (now called genes) controlling traits are present in sexually reproducing organism. These two may be identified or may be different, depending on the percentage. A pattern of inheritance can be worked out with this assumption as shown in figure.

In this explanation, both TT and Tt are tall plants, while only it is a short plant. Traits like T are called dominant traits, while those that behave like ‘t’ are called recessive traits.

Question 2.

How do Mendel’s experiments show that traits are inherited independently?
Mendel crossed

1. pure breeding tall plants having round seeds and
2. pure breeding short plants having wrinkled seeds.

The plants of F1 generation were all tall with round seeds indicating that the traits of tallness and round seeds were dominant.

While self breeding, of F1 yielded plants with characters of 9 tall round seeded, 3 tall wrinkled seeded, 3 short round seeded and one short wrinkled seeded. Tall wrinkled and short round seeded plants are new combinations which can develop only when the traits are inherited independently.

Question 3.
A man with blood group A marries a woman with blood group C and their daughter has blood group O. Is this information enougl to tell you which of the traits – blood group A or O – is dominant? Why or why not?
From this information, it is not possible to tell which of the traits-blood group A or O is dominant. AA group becomes AO. So this information is complete.

Question 4.
How is the sex of the child determined in human beings?
Pair of sex chromosomes determines the particular sex of a child. In human, the males have one X and one Y chromosome and the females have two X chromosomes therefore, the females are XX and the males are XY. The gametes receive half of the chromosomes. The child gametes have 22 autosomes and either X or Y sex chromosome in males while X in females.
Type of male gametes: 22 + X Or 22 + Y.
Type of female gamete: 22 + X.
This is the basis of sex determination in human beings.

Class 10th Science Chapter 9 Intext questions Page No. 150

Question 1.
What are the different ways in which individuals with a particular trait may increase in a population?
A big reason could be accurate copying of DNA and limited variations. Variation causes in generation of new traits and non preserving of existing parental traits. Individuals with a particular trait may also increase due to natural selection that is trait offers some survival advantage. Genetic drift which is caused by genes governing that trait become common in a population.

Question 2.
Why are traits acquired during the life-time of an individual not inherited?
Variation is not hereditary from generation to generation. In case of Asexual reproduction DNA will not transfer to germ cells. So experiences of an individual during its lifetime cannot be passed on to its progeny and cannot direct evolution.

Question 3.
Why are the small numbers of survivingjigers a cause of worry from the point of view of genetics?
Tigers are adopted to their environment as per genes. If tigers number is decreasing number of genes also decrease. So its generation is becoming less.

Class 10th Science Chapter 9 Intext Questions Page No. 151

Question 1.
What factors could lead to the rise of a new species?
Variations, non copying of DNA, natural selection, genetic drift and acquisition of traits during the life time of an individual can give rise to new species.

Question 2.
Will geographical isolation be a major factor in the speciation of a self-pollinating plant species? Why or why not?
Geographical isolation will not a major factor in the speciation of a self pollinating plant species, because self pollination is taking place in one plant. In cross pollination it is a major factor.

Question 3.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not?
Geographical isolation will not be a major factor in the speciation of an organism that reproduces asexually because it is a major factor in organisms that reproduces sexually.

Class 10th Science Chapter 9 Intext Questions Page No. 156

Question 1.
Give an example of characteristics being used to determine how close two species are in evolutionary terms.
The characteristics in different organisms would be similar because they are inherited from a common ancestor. As an example, consider the fact that mammals have four limbs, as do birds, reptiles and amphibians. The basic structure of the limbs is similar through it has been modified to perform different functions in various vertebrates. Such a homologous characteristic helps to identify an evolutionary relationship between apparently different species.

Question 2.
Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?
The wing of a butterfly and the wing of a bat be is not considered homologous organs because the designs of the two wings, their structure and components are very different.

Question 3.
What are fossils? What do they tell us about the process of evolution?
Fossils are the remains of organisms that once existed on earth.

We can gather information about the development of the structures from simple structured to complex structured organisms. They tell us about the phases of evolutions through which they must have undergone in order to sustain themselves in the competitive environment.

Class 10th Science Chapter 9 Intext Questions Page No. 158

Question 1.
Why are human beings who look so different from each other in terms of size, colour and looks said to belong to the same species?
Ans.
A species is a group of organisms that are capable of interbreeding to produce a fertile offspring. Skin colour, looks and size are all variety of features present in human beings. These features are genetic but also environmentally controlled. Various human races are formed based on these features. All human races have more than enough similarities to be classified as same species. Therefore, all human beings are a single species as humans of different colour, size and looks are capable of reproduction and can produce a fertile off spring.

Question 2.
In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better’ body design? Why or why not?
Bacteria is a better body design, because even though it a simple organism, it can survive in hot springs, at the bottom of sea and even in coldest ice covered place such as Antarctica.

### MP Board Class 10th Science Chapter 9 NCERT Textbook Exercises

Question 1.
A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as:
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw
(c) TtWW. Genetic make up of tall plant.

Question 2.
An example of homologous organs is:
(a) our arm and a dog’s fore-leg.
(b) our teeth and an elephant’s tusks.
(c) potato and runners of grass.
(d) all of the above.
(d) Both organs in all option have same basic structural design but have different functions and appearance.

Question 3.
In evolutionary terms, we have more in common with:
(a) a Chinese school-boy
(b) a chimpanzee
(c) a spider
(d) a bacterium
(a) a Chinese school-boy.

Question 4.
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
No, we cannot say anything about whether the light eye colour trait is dominant or recessive. As this information is not sufficient. For considering a trait as dominant or recessive, we need data of at least last three generations.

Question 5.
How are the areas of study – evolution and classification – interlinked?
An example will help with this A brother and a sister are closely related. They have common ancestors in the first generation before them, namely their parents. A girl and her first cousin are also related, but less than the girl and her brother. This is because cousins have common ancestors, their grandparents, in the second generation before them, not in the first one. We can now appreciate that classification of species is in fact a reflection of their evolutionary relationship.

Question 6.
Explain the terms analogous and homologous organs with examples.

Consider the fact that mammals have four limbs, as do birds, reptiles and amphibians. The basic structure of the limbs is similar though it has been modified to perform different functions in various vertebrates. This is an example of homologous characteristic.

We find that the wings of bats are skin folds stretched mainly between elongated fingers. But the wings of birds are feathery covering all along the arm. The design of the two wings, their structure and components, are thus very different. They look similar because they have a common use for flying, but their origins are not common. This makes them analogous characteristics, rather than homologous characteristics.

Question 7.
Outline a project which aims to find the dominant coat colour in dogs.
There are variety of genes that govern coat colour of a dog. At least eleven identified gene series (A, B, C, D, E, F, G, M, P, S, T) that influence coat colour in dog.

A dog inherits one gene from each of its parents. The dominant gene gets expressed in the phenotype. For example, in the B series, a dog can be genetically black or brown.

Let us assume that one parent is homozygous black (BB), while the other parent is homozygous brown (bb)

In this case, all the off springs will be heterozygous (Bb).
Since black (B) is dominant, all the offsprings will be black. However, they will have both B and b alleles.
If such heterozygous pups are crossed, they will produce 25% homozygous black (BB), 50% heterozygous black (Bb), and 25% homozygous brown (bb) offsprings.

Question 8.
Explain the importance of fossils in deciding evolutionary relationships.
Analysis of the organ structure in fossils allows us to make estimates of how far back evolutionary relationships go. The wild cabbage plant is a good example. Humans have over more two thousand years, cultivated wild cabbage as a food plant, and generated different vegetables from it by selection. This is of course, artificial selection rather than natural selection. Kale, cauliflower. Broccoli, cabbage, Red cabbage and Kohl rabi all these have same ancestor.

Question 9.
What evidence do we have for the origin of life from inanimate matter?
As we all know, that there occurs a time when our planet was lifeless, at that time intial matter to develop life was water, sand and some atmospheric gases as CO2, CH4 and nitrogen. The evidence for the origin of life from inanimate matter, was provided through an experiment, conducted in 1953, by Stanley L. Miller and Harold C. Urey. In experiment, they assembled an atmosphere containing molecules like ammonia, methane and hydrogen sulphide, but not oxygen.

This was similar to atmosphere that existed on early earth . This was maintained at a temperature just below 100°C and sparks were passed through the mixture of gases to simulate lightning. At the end of a week, 15% of the carbon from methane, had been converted to simple compounds of carbon including amino acids which make up protein molecules and support the life in basic form.

Question 10.
Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?

Change in on-reproductive tissues cannot be passed on to the DNA of the germ cell. Therefore the experiences of an individual during its lifetime cannot be passed on to its progeny and cannot direct evolution.

Ex: If we breed a group of mice, all their progeny will have tails, as expected. Now, if the tails of these mice are removed by surgery in each generation, do these tailless mice have tailless progeny? The answer is no and it makes sense because removal of the tail cannot change the genes of the germ cells of the mice. Hence sexual reproduction gives rise to more viable variations than asexual reproduction.

Question 11.
How is the equal genetic contribution of male and female parents ensured in the progeny?
Genetic inheritance begins at the time of conception, progeny inherited 23 chromosomes from female parent and 23 from male parent. Together it form 22 pairs of autosomal chromosomes and a pair of sex chromosomes (either XX in case of female, or XY in male). Homologous chromosomes have the same genes in the same positions, but may have different alleles (varieties) of those genes. An individual has two copies of alleles, and that can be homozygous (both copies the same) or heterozygous (the two copies are different) for given gene.

Hence, in human beings, equal genetic contribution of male and female parents is ensured in the progeny through inheritance of equal number of chromosomes from both parents. Females have a equal pair of two X sex chromosomes and males have a pair of one X and one Y sex chromosome. As fertilisation takes place, the male gamete (haploid) fuses with the female gamete (haploid) resulting in formation of the diploid zygote. The zygote in the progeny receive an equal contribution of genetic traits from the parental generations.

Question 12.
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?
Only variations that confer an advantage to an individual organism will survive in a population we agree to this statement variation is convenient for survival. This provides diversity for organisms.

### MP Board Class 10th Science Chapter 9 Additional Important Questions

MP Board Class 10th Science Chapter 9 Multiple Choice Questions

Question 1.
Fossil archaeopteryx exhibits connection between:
(a) Amphibian and fish
(b) Reptiles and fish
(c) Reptile and birds
(d) Birds and mammals
(c) Reptile and birds

Question 2.
The sex of the human child depends on the sex chromosome present in the:
(a) Egg
(b) Spenn
(c) Both (a) and (b)
(d) None of these
(b) Spenn

Question 3.
Genetic information is carried out by long chain of molecules made up of:
(a) Enzymes
(b) DNA
(c) Amino acids
(d) Proteins
(b) DNA

Question 4.
Which one of the following represents a ratio of monohybrid cross?
(a) 9 : 7
(b) 3 : 1
(c) 1 : 1 : 1 : 1
(d) 9 : 3 : 3 : 1
(b) 3 : 1

Question 5.
On which plant Mendel carried his experiments of inheritance?
(a) Cow pea
(b) Wild pea
(c) Garden pea
(d) Pigeon pea
(c) Garden pea

Question 6.
A gamete certains which of the following?
(a) Both alleles of a gene
(b) Only one allele of a gene
(c) All alleles of a gene
(d) No allele of a gene
(b) Only one allele of a gene

Question 7.
Chromosomes are made up of
(a) Proteins
(b) DNA
(c) RNA
(d) All of these.
(d) All of these.

Question 8.
Pea plants were more suitable than cats for Mendel’s experiments because:
(a) Cats have many genetic traits
(b) No pedigree record of cats
(c) Pea plants can be self-pollinated or fertilised
(d) Pea plants favour cross pollination.
(c) Pea plants can be self-pollinated or fertilised

Question 9.
In a cross Tt × Tt, the percentage of offsprings produced having same phenotype as the parents would be:
(a) 50%
(b) 100%
(c) 25%
(d) 0%
(a) 50%

Question 10.
Who proposed the laws of heredity?
(a) Darwin
(b) Mendel
(c) Morgan
(d) Dalton
(b) Mendel

MP Board Class 10th Science Chapter 9 Very Short Answer Type Questions

Question 1.
Define heredity.
The process by which traits and characteristics are reliably inherited or passed from the parents to the offspring is called heredity.

Question 2.
What is a gene?
Gene is a functional segment of DNA on a chromosome occupying specific position, which carries out a specific biological function.

Question 3.
Name the plant on which Mendel performed his experiments.
Garden pea (Pisum sativum).

Question 4.
Define the term variation.
Variation: There are differences found in structure, function, behaviour and genetic make up of different individuals of the same parentage, variety, race and species. These differences refer to variation.

Question 5.
Write the expanded form of DNA.
Deoxyribonucleic acid (DNA).

Question 6.
Define genetics.
The branch of biology which deals with heredity and variations, is known as genetics.

Question 7.
Define the term offspring.
Offspring is an individual formed as a result of sexual reproduction involving the formation and fusion of two gametes. The genotype of an offspring is different from either of the parents due to shuffling of chromosomes and their genes.

Question 8.
What are reciprocal crosses?
They are two types of crosses involving two groups of individuals where the male of one group is crossed with the female of the other and vice versa.

Question 9.
Where are the genes located? What is the chemical nature of gene?
Genes are located at a specific position on a chromosome. Chemical Nature of Gene: Chemically, gene is a segment of deoxyribonucleic acid (DNA) consisting of specific sequence of the nucleotides. The sequence of the constituent nucleotides determines the functional property of a gene.

MP Board Class 10th Science Chapter 9 Short Answer Type Questions

Question 1.
Define genetics. What is the contribution of Mendel in this branch of Biology?
Genetics is the branch of science of heredity and variations which deals with the study of the transmission of traits from parents to the offsprings and the occurrence of differences among the individuals.

Contribution of Mendel: Mendel did his experiments on garden pea (Pisum sativum) and discovered the scientific principles, which govern patterns of inheritance i.e., the principle of inheritance. He explained that contrasting characters are controlled by units which he called ‘Factors Today, these factors are called genes.

Question 2.
Differentiate between inherited and acquired traits.
Inherited traits:

1. The traits which are inherited from the parents (Father and Mother) to the offsprings (progeny) are called inherited traits.
2. These traits are due to genetic make up of the progeny.

Acquired characters

1. These traits cannot be passed on to their future generations.
2. These traits develop in response to the environment.

Question 3.
What are Mendel’s laws of inheritance?
Law of dominance: When two homozygous individuals with one or more sets of contrasting characters are crossed the characters that appear in the F, hybrids are dominant characters.

Law of segregation: Contrasting characters brought together in hybrid remain together without being contaminated and when gametes are formed from the hybrid, the two separate out from each other and only one enters each gamete.

Law of independent assortment: In inheritance of more than one pair of contrasting characters simultaneously, the factors for each pair of characters assort independently of other pair’s.

Question 4.
How did life originate on earth?
Life originated on earth from inorganic elements and compounds under extreme atmospheric conditions (such as very high temperature, electric discharges, reducing atmosphere etc.) by formation of complex organic compounds such as amino acids.

Question 5.
Why did Mendel choose garden pea for his experiments?
Due to the following reasons, Mendel selected garden pea for his experiment:

1. Garden pea flowers are normally self-pollinated but can be easily cross-pollinated.
2. Many varieties with distinguished contrasting characters e.g., smooth seed coat, wrinkled seed coat are available.
3. A large number of progeny can be produced in a short duration.
4. Its flowers can be easily handled for experimentation.

Question 6.
What are the factors which help in speciation?

1. Genetic drift: Due to genetic drift, there will be accumulation of # different changes in each sub-populations. The levels of gene flow ’ between them will decrease if they are further isolated, it will be more on a small sub-population.
2. Over generations, genetic drift will accumulate, causing different changes in the populations.
3. Natural selection may also operate differently in the different geographical location.
4. Together, genetic and natural selection will make the population more and more different from each other. As a result, members will be incapable of reproducing with each other. Changes may be due to change in DNA or number of chromosomes.

Question 7.
Does geographical isolation of individuals of a species lead to formation of a new species? Provide a suitable explanation.
Yes, geographical isolation of sub-populations of a population of a species leads to genetic drift. This may impose limitations to.sexual reproduction of the separated population. Slowly, the separated individuals will reproduce among themselves and generate new variations. Continuous accumulation of those variations through a few generations may ultimately lead to the formation of a new species.

Question 8.
What tools have been used to study human evolution?
The tools used for tracing evolutionary line are:

1. Excavating time – dating and study of fossils.
2. Determining DNA sequences.

MP Board Class 10th Science Chapter 9 Long Answer Type Questions

Question 1.
A husband have 46 chromosomes, his wife has 46 chromosomes. Then, why don’t their offspring have 46 pairs of chromosomes, which is obtained by the fusion of male and female gametes? Support your answer with a neat illustration.
At the stage of gamete formation, meiosis division (reduction division) occurs. As a result, each gamete receives half number of chromosomes of the parent. So, when male gamete (sperm) fuses with egg, original number of chromosomes of the parent is received by the zygote.

Fertilisation

Question 2.
Name the characters studied by Mendel in garden pea.

Question 3.
Explain the terms:
Monohybrid cross, dihybrid cross, monohybrid ratio and dihybrid ratio.
Monohybrid cross: Monohybrid cross is that cross which is made to study the inheritance of a single pair of genes or factors of a character.

Dihybrid cross: It is a cross which is made to study the inheritance of two pairs of genes or two characters.

Monohybrid ratio: It is the ratio which is obtained in the F2 generation when a monohybrid cross is made. It is usually 3 : 1 (Phenotypic ratio) or 1 : 2 : 1 (genotypic ratio).

Dihybrid ratio: It is the ratio, which is obtained in the F2 generation when a dihybrid cross is studied. It is usually 9 : 3 : 3 : 1 (phenotypic ratio).

Question 4.
Describe any three methods of tracing evolutionary relationships among organisms.
The following methods help us in tracing evolutionary relationships:

(i) Study of homologous organs: Organs which have similar structure and origin are called homologous organs. For example: limbs of birds, frog, human may look different but they have similar structure and origin. Such homologous organs help to identify an evolutionary relationship between apparently diffejent species.

(ii) Study of analogous organs: Analogous organs are similar in function but differ in structure and origin. For example’. forelimbs of birds and bats are used for flying but their origins and components are not common. Thus, study of analogous organs reveals difference in their ancestry and their evolutionary relationship.

(iii) Study of fossils: All impressions, casting of body or hard remains of ancient life in the sedimentary rocks are called fossils. Study of fossils helps in finding out:
(a) Interrelationship of ancient life.
(b) Correlation of forms of life existing today and their line of evolution from ancient life.

Question 5.
A tall pea plant bearing violet flowers is crossed with short pea plant bearing white flowers. Work out the F1 and F2 generations. Give F2 ratio.
Parents: Tall pea plant with violet flower × Short pea plant with white flower

Question 6.
Given below is the experiment carried out by Mendel to study inheritance of two traits in garden pea:
(а) What do A, B, C, D, E, F and G represent in these boxes?
(b) State the objective for which Mendel performed this experiment.

Independent inheritance of two separate traits, shape, and colour of seeds.
(a) A = gamete (Ry) of round green plant.
B = gamete (rY) of wrinkled yellow plant.
C = (RrYy).
D = 9, E = 3, F = 3, G = 1.
(b) To show independent inheritance of traits or to prove law of independent assortment.

### MP Board Class 10th Science Chapter 9 NCERT Textbook Activities

Class 10 Science Activity 9.1 Page No. 143

Observe the ears of all the students in the class. Prepare a list of students having free or attached earlobes and calculate the percentage of students having each (Fig. 9.1). Find out about the earlobes of the parents of each student in the class. Correlate the earlobe type of each student with that of their parents. Based on this evidence, suggest a possible rule for the inheritance of earlobe types.

(a) Free and (b) attached earlobes. The lowest part of the ear, called the earlobe, is closely attached to the side of the head in some of us, and not in others. Free and attached earlobes are two variants found in human populations.

Observations:

• Earlobes can be free or attached. The genes for earlobe inheritance consists of two alleles. Both the alleles for attached and free earlobes can be present in a single human being, the one which is dominant shows and the recessive one do not express itself,

Class 10 Science Activity 9.2 Page No. 144

• In Fig. 9.2, what experiment would we do to confirm that the F2 generation did in fact have a 1 : 2 : 1 ratio of TT, Tt and tt trait combinations?

Inheritance of traits over two generations.

Observations:
The cross fertilisation of pea plants showing different traits can be done at F2 stage and the number of plants for particular trait (height here) can be studied and used to confirm 1 : 2 : 1 ratio of TT, Tt and it

## MP Board Class 10th Science Solutions Chapter 14 Sources of Energy

### MP Board Class 10th Science Chapter 14 Intext Questions

Class 10th Science Chapter 14 Intext Questions Page No. 243

Question 1.
What is a good source of energy?
We could then say that a good source of energy would be one.

1. Which would do a large amount of work per unit volume or mass.
2. be easily accessible.
3. be easy to store and transport, and
4. perhaps most importantly, be economical.

Question 2.
What is a good fuel?
A good fuel is one which

• produces more heat per unit mass. It has high calorific value.
• produces less harmful gases on combustion.
• is cheap and easily available.
• is every to handle safe to transport and convenient to store.

Question 3.
If you could use any source of energy for heating your food, which one would you use and why?
We should select which is easily available and it should be cheaper. Bio-gas is an excellent fuel as it contains. It burns without some. Its heating capacity is high. This gas is convenient for consumption and transportation.

Class 10th Science Chapter 14 Intext questions Page No. 248

Question 1.
What are the disadvantages of fossil fuels?
Disadvantages of fossil fuels are as following:

1. Fossil fuels are limited source and we can not use them for more than 110-120 years. From not so designing or making machines dependent on them will be a big failure after their loss.
2. Fossil fuel generates big amount of pollution which will destroy our atmosphere and increase temperature of earth which lead to destruction of our ecosystem.

Question 2.
Why are we looking at alternate sources of energy?
Fossil fuels are a non-renewable source of energy. So we need to conserve them. If we were to continue consuming these sources at such alarming rates, we would soon run out of energy. In order to avoid this, alternate sources of energy were explored.

Question 3.
How has the traditional use of wind and water energy been modified for our convenience?
(1) Wind energy: The kinetic energy of the wind can be used to do work. This energy was harnessed by wind mills in the past to do mechanical work. For example in a water lifting pump, the rotatory motion of windmill is utilized to lift water from a well. Today wind energy is also used to generate electricity. A windmill essentially consists of a structure similar to a large electric fan that is erected at some height on a rigid support.

A number of windmills are erected over a large area, which is known as wind energy farm. The energy output of each windmill in a farm is coupled together to get electricity on a commercial scale wind energy farms can be established only at those places where wind blows for the greater part of a year. The wind speed should also be higher than 15 km/h to maintain the required speed of the turbine, since, the tower and blades are exposed to the vagaries of nature like rain, sun, storm and cyclone, they need a high level of maintenance.

(2) Water energy: In order to produce hydel electricity, high rise dams are constructed on the river to obstruct the flow of water and thereby collect water in larger reservoirs. The water level rises and in this process the kinetic energy of flowing water gets transformed into potential energy. The water from the high level in the dam is carried through pipes, to the turbine, at the bottom of the dam. Sine the water in the reservoir would be refilled each time. It rains (hydropower is a renewable source of energy) we would not have to worry about hydro electricity sources getting used up the way fossil fuels would get finished one day.

Class 10th Science Chapter 14 Intext Questions Page No. 253

Question 1.
Can any source of energy be pollution free? Why or why not?
Yes, nature show itself some examples of energy conversion which arg pollution free as photosynthesis, as we know in this process photo energy is converted to chemical energy. Hence, solar energy is best way to produce pollution free energy.

Question 2.
Hydrogen has been used as rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Yes, it is cleaner because it does not create any residual hazardous product or chemicals which pollute environment or disbalance the ecosystem. But, handling such big amount of energy properly is required.

Class 10th Science Chapter 14 Intext Questions Page No. 254

Question 1.
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Energy derived from water, wind, sun and ocean all are renewable. All these energies can be harnessed into usable form as long as the solar system exists.

Question 2.
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.

• fossil fuels
• Nuclear fuels

Fossil fuels are present in a limited. amount in the earth. Once exhausted, they will not be available to us again. It takes millions of years for fossil fuel to be formed. The nuclear materials which can be conveniently extracted from earth 7. are limited and hence they will get exhausted one day.

Class 10th Science Chapter 14 NCERT Textbook Exercises

Question 1.
A solar water heater cannot be used to get hot water on:
(a) A sunny day
(b) A cloudy day
(c) A hot day
(d) A windy day
(b) A cloudy day

Question 2.
Which of the following is not an example of a bio-mass energy source?
(a) Wood
(b) Gobar-gas
(c) Nuclear energy
(d) Coal
(c) Nuclear energy

Question 3.
Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the sun’s energy?
(a) Geothermal energy
(b) Wind energy
(c) Nuclear energy
(d) Bio-mass
(c) Nuclear energy

Question 4.
Compare and contrast fossil fuels and the sun as direct sources of energy.

Question 5.
Compare and contrast bio-mass and hydro electricity as sources of energy.

Question 6.
What are the limitations of extracting energy from—
(a) the wind?
(b) waves?
(c) tides?
(a) The wind:

1. Wind energy farms can be established only at those places where wind blows for the greater part of a year.
2. The wind speed should also be higher than 15 km/h to maintain the required speed of the turbine.
3. Establishment of wind energy farms require large are of land.

These are the limitations of extracting energy from the wind.

(b) Limitations of extracting waves energy: The waves are generated by strong winds blowing across the sea. Wave energy would be a viable proposition only where waves are very strong.

(c) Limitations of extracting tidal energy: The locations where such dams can be built are limited.

Question 7.
On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?
The options given in (a) and (b) are the same.

Question 8.
What are the qualities of an ideal source of energy?
The qualities of an ideal source of energy are as follows:

1. Which would do a large amount of work per unit volume or mass.
2. Be easily accessible.
3. Be easy to store and transport, and
4. Perhaps most importantly, be economical.

Question 9.
What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Solar cooker is a device used to trap solar energy and utilize it to cook food. It consists of a box painted black from inside to absorb heat of the Sun (black colour is the best absorber of heat). A thick glass lid is placed over the box to trap heat energy of the sun. A plane mirror reflector is also attached to the box so that a strong beam of sunlight falls over the cooker’s top.

The reflector of the solar cooker sends strong beams of sunlight over the top of the cooker. Sunlight consists of about 1/3 rd infra-red rays which have a heating effect. These infra-red rays are of shorter wavelength as these are produced by a very hot source of heat. The glass lid over the cooker allows these infra-red rays of short wavelength into the cooker but does not allow the infra-red rays which are emitted by the black surface of the cooker to escape as these are of longer wavelength. Thus, heat energy of the sun gets trapped in the black box of the solar cooker. This heat cooks the food material kept in the black box.

Fig. 14.1: Solar heating device (solar cooker).

Advantages of solar cooker:

1. It is used to cook food and saves precious fossil fuel.
2. It does not cause any pollution.
3. No smoke is produced during the working of a solar cooker.
4. Nutrients of food material, which is to be cooked in the solar cooker, do not get destroyed.
5. Four food items can be cooked at the same time.

1. It cannot be used to cook food during the night.
2. It cannot be used to cook food on a cloudy day.
3. The direction of the reflector has to be changed after a small interval of time with the change of position of the sun.

Question 10.
What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
They are:

• Burning of fossil fuels to meet the increasing demand for energy causes air pollution.
• Construction of dams and rivers to generate hydroelectricity destroys large ecosystems which get submerged underwater in the dams further, a large amount of methane [which is a green house gas] is produced when submerged vegetation rots under anaerobic conditions.

In order to reduce energy consumption

• Fossil fuel should be used with care and caution to derive maximum benefit out of them.
• Fuel saving devices such as pressure cookers etc should be used.
• Efficiency of energy sources should be maintained be getting them regularly serviced.
• And last of all, we should be economical in our energy consumption as energy saved is energy produced.

### MP Board Class 10th Science Chapter 14 Additional Important Questions

MP Board Class 10th Science Chapter 14 Multiple Choice Questions

Question 1.
Can we convert any form of energy to its other form?
(a) Yes
(b) No
(c) May be Yes
(d) None
(a) Yes

Question 2.
Photosynthesis represents what kind of conversion of energy:
(a) Conversion of photo-energy to chemical energy
(b) Conversion of chemical energy to photo-energy
(c) Conversion of physical energy to photo-energy
(d) Conversion of chemical energy to electrical energy
(a) Conversion of photo-energy to chemical energy

Question 3.
Which one of the following is good source of energy?
(a) Burning wood
(b) Burning cooking oil
(c) Burning wax
(d) Burning petroleum
(d) Burning petroleum

Question 4.
Fuel not used for cooking is:
(a) LPG
(b) Coal
(c) Petrol
(d) PNG
(c) Petrol

Question 5.
Renewable source of energy is:
(a) Diesel
(b) Water
(c) Coal
(d) Petrol
(b) Water

Question 6.
Physical energy is changed to electrical energy in:
(a) Thermal power plant
(b) Hydro power plant
(c) Photosynthesis
(d) None
(a) Thermal power plant

Question 7.
Which one among following is not a property of biomass fuel?
(a) It contains 75% methane
(b) Bum without smoke
(c) Leaves no residue
(d) Easy to install
(c) Leaves no residue

Question 8.
What kind of energy is used in wind energy form?
(a) Potential energy
(b) Kinetic energy
(c) Chemical energy
(d) Photo-energy
(b) Kinetic energy

Question 9.
Which one is among alternative non-conventional source of energy?
(a) Fossil fuel
(b) Biomass
(c) Solar energy
(d) None of these
(c) Solar energy

Question 10.
What percent of total of solar energy is absorbed on earth:
(a) 10%
(b) 50%
(c) 100%
(d) Can’t calculate
(a) 10%

Question 11.
Ultimate source of energy on earth is:
(a) Electricity
(b) Nuclear energy
(c) Fossil fuel
(d) Sun
(d) Sun

Question 12.
To maintain a wind energy farm, the wind speed should be:
(a) 1-2 km/h
(b) 180-200 km/h
(c) 15-20 km/h
(d) Can’t be calculated
(c) 15-20 km/h

Question 13.
Which of the following element is chosen for generating nuclear energy?
(a) Uranium
(b) Silicon
(c) Germanium
(d) Carbon
(c) Germanium

Question 14.
How bio gas is generated in biomass plant?
(a) By distillation
(b) By anaerobic fermenting
(c) By reduction
(d) By simple burning
(b) By anaerobic fermenting

Question 15.
Natural gas contains:
(a) CO2
(b) H2O
(c) CH4
(d) NH3
(c) CH4

Question 16
…………. is used in a solar cell for storing energy.
(a) Gold
(b) Silver
(c) Germanium
(d) Silicon
(d) Silicon

Question 17.
The stored heat in the earth is harnessed as:
(a) Fuel
(b) Geothermal energy
(c) Solar energy
(d) Biomass
(b) Geothermal energy

Question 18.
Main constituent of LPG is:
(a) Butane
(b) Methane
(c) Propane
(d) Ethane
(c) Propane

Question 19.
High calorific value of a material represents:
(a) A good manure
(b) A good fuel
(c) Protein rich material
(d) A good conductor of electricity
(b) A good fuel

Question 20.
…………………… is a coal with highest carbon content
(a) Bituminous
(b) Peat
(c) Anthracite
(d) None
(c) Anthracite

MP Board Class 10th Science Chapter 14 Very Short Answer Type Questions

Question 1.
Name two things which are considered as good source of energy.
Coal and petrol.

Question 2.
Write a main characteristic of a good fuel.
It should release a large amount of energy per unit volume.

Question 3.
Which food product can be used to produce light energy?
Cooking oil and fodder.

Question 4.
What kind of energy source can be used with the help of concave mirror?
Solar energy when being used in solar appliances.

Question 5.
What kind of energy is heat energy of molten rock present inside earth core?
Geothermal energy.

Question 6.
Name two energy sources which are conventional and renewable in nature.
Biomass and hydroelectricity.

Question 7.
Write one limitation of use of fossil fuels.
Pollution.

Question 8.
How much percent of CH4 is present in Bio gas?
75%.

Question 9.
Write two kind of solar energy manifestation to oceans.
Wave energy and ocean thermal energy.

Question 10.
What percentage of nuclear energy is contributed in total energy production in India?
Approximately 3-4%.

Question 11.
What is main source of solar energy?
Sun is the main source of energy.

Question 12.
Give one cause of limitation of solar energy.
Solar energy is costly.

Question 13.
What is nuclear energy?
Nuclear fission is the process during which two nucleus fuse to form one nucleus. The energy which is produced in this process called nuclear energy.

Question 14.
Give three examples of energy which is produced from sea.
Tidal Energy, wave energy and Ocean thermal energy.

MP Board Class 10th Science Chapter 14 Short Answer Type Questions

Question 1.
Why it is important to consume energy wisely?
When we use energy in its usable form we convert the form of energy and get our work done during the process. Since, we cannot reverse . the change involved in this process so we cannot get back the original usable form of energy. Due to this, it becomes important to think about energy shortage and the related energy crisis.

Question 2.
Write characteristics of a good source of energy.
Characteristics of a good source of energy are:

• It should be effective i.e., able to do large amount of work in mass or volume.
• It should be easily accessible.
• It should be easily transported from one place to other.
• It should be economical.

Question 3.
What are conventional sources of energy?
The sources of energy which have been in knowledge since a long time are conventional sources of energy. Firewood, coal, petroleum, natural gas, hydel energy, wind energy and nuclear energy are considered to be the conventional sources of energy.

Question 4.
Give two examples of fossil fuels.
Two examples of fossil fuels used commercially for producing energy are:

Coal: The plants buried under swamps after death for very long time and due to high pressure and high temperature inside the earth; they are converted into coal. Coal is the highest used energy source in India.

Petroleum: The animals body after death get buried under the ocean surface and due to high pressure and high tempera lure inside the water were converted into petroleum; in due course of time Petroleum is among the major source of energy. Petroleum products are used as automobile fire! and also in the chemical industries.

Question 5.
Differentiate between non-renewable and renewable sources of Energy.
Non-renewable sources of Energy: It takes millions of years for the formation of fossils fuels. Since, they cannot be replenished in the foreseeable future, they are known as non-renewable sources of energy.

Renewable sources of Energy: Those sources of energy which can be replenished quickly are called renewable sources of energy. Hydel energy, wind energy and solar energy are examples of renewable sources of energy.

Question 6.
What is hydel energy?
Hydel Energy: Hydel energy is produced by utilizing the kinetic energy of flowing water. Huge dams are built over a source of water. Water is collected behind ‘the dam and released. When the water falls on the turbine; the turbine moves; because of kinetic energy of water. Electricity is generated by the turbine. Electricity; thus generated is called hydel energy of hydroelectricity. Water in the reservoir is replenished with rainwater and so, availability of water is, not a problem for hydroelectricity.

Question 7.
How electricity is generated in thermal power plant?
In a thermal power plant, coal or petroleum is used for converting water into steam. The steam is used to run the turbine and thus, electricity in generated.

Question 8.
Define biomass.
Biomass: The plants and animals constitute the biomass. Farm waste; such as stalks of harvested plants and dung of cattle; can be used to generate methane. The decomposition of biomass produces methane; which can be channelized for useful purposes.

Question 9.
What is bio-gas plant? How it is channelized?
Bio-gas plant: Bio-gas plant can be very useful in solving the energy need of rural areas. A bio gas plant is a dome like structure which is usually built from bricks and concrete. In the mixing tank; the slurry is made from cow dung and water. The slurry then goes to the digester; which is a closed chamber. Since oxygen is absent in the digester, the anaerobes carry on their work of decomposition. The process of decomposition produces bio gas. Bio gas has about 70% of methane and the rest is composed of other gases.

The bio gas is channelized through a pipe and can be utilitzed as kitchen fuel and also as fuel for getting light. The slurry; left behind; is removed. It is used as manure, once it dries.

Question 10.
What is wind energy?
Wind energy has been in use since ages. The sail boats of the pre-industrialisation era used to run on wind power. Windmills have been in use; especially in Holland; since the medieval period. Nowadays, windmills are being used to generate electricity. The kinetic energy of wind is utilized to run the turbines; which generate electricity.

Question 11.
What is non-conventional sources of energy?
Energy sources which are relatively new are called non-conventional sources of energy, e.g., nuclear power and solar energy.

Question 12.
Explain solar energy.
The sun is the main source of energy for all living beings on this earth. Even the energy in the fossil fuels has come from the sun. The sun is an endless reservoir of energy which would be available as long as the solar system is in existence. Technologies for harnessing the solar energy have been developed in recent times.

Question 13.
What is solar cooker and how food is cooked in it?
Solar cooker is very simple in design and mode of function. It is usually made from mirrors. Plane mirrors are placed inside a rectangular box. The light reflected from the plane mirrors concentrates the solar energy inside the solar cooker which generates enough heat to cook food.

Question 14.
What are solar cells?
Solar cells: Solar cells are made from silicon. The solar panel converts solar energy into electrical energy which is stored in a battery; for later use.

Question 15.
What is tidal energy?
Due to the gravitational pull of the moon, tides happen near seashores. Water rushes up near the seashore during a high tide and goes down during a low tide. Dams are built near seashores to collect the water which comes during a high tide. When the water runs back to the ocean, the flow of water can be utilized to generate electricity.

Question 16.
How energy is generated from molten rocks?
The molten rocks from the inside the earth are pushed in certain regions of the earth. Such regions are called the hot spots of the earth. When groundwater comes in contact with such hot spots, lot of steam is generated. This steam can be harnessed to produce energy which is called Geothermal Energy.

Question 17.
What is nuclear energy?
Nuclear fission is the process during which two nucleus fuse to form one . nucleus. The process generates a huge amount of energy. This phenomenon is utilized in nuclear power plants. Nuclear power is safest for the environment but the risk of damage due to accidental leaks of radiation is pretty high. Further, storage of nuclear waste is a big problem because of potential risk of radiation involved. Nonetheless, many countries are using nuclear power in a big way.

MP Board Class 10th Science Chapter 14 Long Answer Type Questions

Question 1.
Define biomass. What is Bio gas plant? How it is channelized?
Biomass: The plants and animals constitute the biomass. Farm waste; such as stalks of harvested plants and dung of cattle; can be used to generate methane. The decomposition of biomass produces methane; which can be channelized for useful purposes.

Bio gas plant: Bio gas plant can be very useful in solving the energy need of rural areas. A bio gas plant is a dome like structure which is usually built from bricks and concrete. In the mixing tank; the slurry is made from cow dung and water. The slurry then goes to the digester; which is a closed chamber. Since oxygen is absent in the digester, the anaerobes carry on their work of decomposition. The process of decomposition produces bio gas, has about 70% of methane and the rest ‘is composed of other gases. The bio gas is channelized through a pipe and can be utilized as kitchen fuel and also as fuel for getting light. The slurry; left behind; is removed. It is used as manure, once it dries.

Question 2.
What is wind energy? Write limitations of wind energy.
Wind energy has been in use since ages. The sail boats of the re-industrialization era used to run on wind power. Windmills have been in use; especially in Holland; since the medieval period.

Nowadays, windmills are being used to generate electricity. The kinetic energy of wind is utilized to run the turbines; which generate electricity.

Limitations of wind Energy: Wind farms can only be established at those places where the wind speed is high enough and is more than 15 km/hr for most parts of the year. Wind farms need to be established on large tracts of land. The fan of the windmill has many moving parts; so cost of maintenance and repair is quite high. The fact, that it has to suffer the vagaries of the nature, further compounds the problem. Initial cost of establishing a wind farm is very high.

Question 3.
Briefly explain energy from sea.
Tidal energy: Due to the gravitational pull of the moon, tides happen at seashores. Water rushes up near the seashore during a high tide and goes down during a low tide. Dams are built near seashores to collect the water which comes during a high tide. When the water runs back to the ocean, the flow of water can be utilized to generate electricity.

Wave Energy: Waves can also be a good source of energy. Many devices are being designed and tested to produce wave energy. For example; a hollow tower is built near the seashore. When water gushes in the tube because of wave, it forces the air upwards. The kinetic energy of air in the tube is used to run a turbine. When the wave goes down; air from up goes down the tube which is also used in running the turbine.

Ocean Thermal Energy. The water at sea surface is hot during daytime, while the water at lower level is cold. The temperature differential in water levels can be utilized to generate energy. If the temperature differential is more than 20°C, then ocean thermal energy can be utilized from that place. For this, a volatile liquid; like ammonia; is boiled using the heat from the hot water at the surface. The steam of the volatile liquid is utilized to run the turbine to generate electricity. Colder water from the surface below is utilized to condense ammonia vapour which is then channelized to the surface to repeat the cycle.

Question 4.
Explain Solar Energy. How is food cooked with help of solar energy and also explain its limitations.
The sun is the main source of energy for all living beings on this earth. Even the energy in the fossil fuels has come from the sun. The sun has an endless reservoir of energy which would be available as long as the solar system is in existence. Technologies for harnessing the solar energy hav been developed in recent times.

Solar cooker is very simple in design and mode of function. It is usually made from mirrors. Plane mirrors are placed inside a rectangular box. The light reflected from the plane mirrors concentrates the solar energy inside the solar cooker which generates enough heat to cook food.

Limitations of solar Energy: The technologies for harnessing solar energy are at a nascent stage. At present, the cost benefit ratio for using solar energy is not conducive. Using solar energy is exhorbitantly costly.

### MP Board Class 10th Science Chapter 14 NCERT Textbook Activities

Class 10 Science Activity 14.1 Page No. 242

• List four forms of energy that you use from morning, when you wake up, till you reach the school.
• From where do we get these different forms of energy?
• Can we call these ‘sources’ of energy? Why or why not?

Observations:

• Forms of energy that we use are electrical energy, mechanical energy, chemical energy for vehicles, chemical energy from food.
• Energy can neither created nor destroyed. It is just transferred from one form to the other.
• The ‘sources’ of energy are the one which releases energy to be used in such forms.

Class 10 Science Activity 14.2 Page No. 243

• Consider the various options we have when we choose a fuel for cooking our food.
• What are the criteria you would consider when trying to categories something as a good fuel?
• Would your choice be different if you lived:

(a) in a forest?
(b) in a remote mountain village or small island?
(c) in New Delhi?
(d) lived five centuries ago?

• How are the factors different in each case?

Observations:

• The criteria for good fuel inducts amount of energy released upon combustion, smoke produced or not, easily accessible, economical and easy be store and transport.
• In forest or remote village, wood from forests can be used as fuel.
• In new Delhi, electrical energy would be a choice.
• Five centuries ago, may be mechanical energy would have been used.
• Factors includes availability of the sunrises and case in utilizing them.

Class 10 Science Activity 14.3 Pages No. 244-245

• Take a table-tennis ball and make three slits into it.
• put semicircular fins cut out a metal sheet into these slits.
• Pivot the tennis ball on an axle through its centre with a straight metal wire fixed to a rigid support. Ensure that the tennis ball rotates freely about the axle.
• Now connect a cycle dynamo to this,
• Connect a bulb in series.
• Direct a jet of water or steam produced in a pressure cooker at the fins (Fig. 14.2). What do you observe?

Fig. 14.2: A model to demonstrate the process – of thermo – electric production.

Observations:

• We observe that fan starts morning. The rotor blade also moves with speed that turn the shaft of the dynamo and concert the mechanical energy into electrical energy.

Class 10 Science Activity 14.4 Page No. 248

• Find out from your grand-parents or other elders:
• (a) how did they go to school?
• (b) how did they get water for their daily needs when they were young?
• (c) what means of entertainment did they use?
• Compare the above answers with how you do these tasks now.
• Is there a difference? If yes, in which case more energy from external sources is consumed? _

Observations:

• Earlier, people used to go school on-foot.
• The water were drawn from wells from far off places and carried on head in pots to the home.
• Means of entertainment includes folk dances, songs etc.
• The scenario has totally changed, nowadays, people are being separately and generally, not in noses as were done decades ago. More energy from internal sources is consumed these days to fulfill the demands of energy which is inversed a lot.

Class 10 Science Activity 14.5 Page No. 249

• Take two conical flasks and paint one white and the other black. Fill both with water.
• Place the conical flasks in direct sunlight for half an hour to one hour.
• Touch the conical flasks. Which one is hotter? You could also measure the temperature of the water in the two conical flasks with a thermometer.
• Can you think of ways in which this finding could be used in your daily life?

Observations:

• The one with black colour is hotter as black absorbs more heat as compared to white one.
• In daily life, we apply this on the colour we wear. The days which are that, we avoid black colours as they absorb more heat. Sincerity for cooling effect, white colours used.

Class 10 Science Activity 14.6 Pages No. 249-250

• Study the structure and working of a solar cooker and/or a solar water- heater, particularly with regard to how it is insulated and maximum heat absorption is ensured.
• Design and build a solar cooker or water-heater using low-cost material available and check what temperatures are achieved in vour system.
• Discuss what would be the advantages and limitations of using the solar cooker or water-heater.

Observations:

• The minimum heat absorption is ensured by painting it black in colour. The glass used on the lop traps the infrared rays from the sun and do not allow them the escape.
• Advantages includes no wastage of energy as solar energy is a trapped to be used further. It is a renewable some of energy that do not create any pollution.
• Limitations includes plausibility of solar rays at certain times of day only. It will not work on sunny days.

Class 10 Science Activity 14.7 Page No. 252

• Discuss in class the question of what is the ultimate source of energy for bio-mass, wind and ocean thermal energy.
• Is geothermal energy and nuclear energy different in this respect? Why ?
• Where would you place hydro electricity and wave energy?

Observations:

• The cleaner source of energy is the sun. Yes, cleaner energy is obtained from fusion or fission of molecules whereas geothermal energy is the energy present in the earth. The energy from geological changes is harnessed to be used in various ways.
• Hydro electricity and wave energy are also form of renewable energy.

Class 10 Science Activity 14.8 Page No. 253

• Gather information about various energy sources and how each one affects the environment.
• Debate the merits and demerits of each source and select the best source of energy on this basis.

Observations:

• Among the various source of energy, renewable sources of energy are the best as they do not harm the environment and this energy can be reused and when required. Non-renewable resources of’energy are harmful to the environment and causes pollution.
• Best sources of energy arc renewable sources of energy like solar, hydro, tidal, wave energy etc.

Class 10 Science Activity 14.9 Page No. 254

• Debate the following two issues in class.

(a) The estimated coal reserves are said to be enough to last us for another two hundred years. Do you think we need to worry about coal getting depleted in this case? Why or why not?
(b) It is estimated that the Sun will last for another five billion years. Do we have to worry about solar energy getting exhausted? Why or why not?

• One the basis of the debate, decide which energy sources can be considered
1. exhaustible
2. inexhaustible
3. renewable
4. non-renewable.

Give your reasons for each choice.

Observations:

• Yes, we need to worry about availability of coal as resources are limited they are made from fossil fuels which take millions of years to be formed. Also, they cause pollution and harm the environment.
• Sun will least for another five billion years but we should use this to the maximum as there are still so many years in which it can be utilized, harness eat and stored.
• Exhaustible are those energy sources which will get exhausted soon from fossil fuel inexhaustible are the one like solar, tidal etc. Renewable can be used whereas non-renewable are not used again and again.

## MP Board Class 10th Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3

In this article, we will share MP Board Class 10th Maths Book Solutions Chapter 13 Surface Areas and Volumes Ex 13.3 Pdf, These solutions are solved subject experts from the latest edition books.

## MP Board Class 10th Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.3

Take π = $$\frac{22}{7}$$, unless stated otheriwise

Question 1.
A metallic sphere of radius 4.2 cm is melted and recast into the shape of a cylinder of radius 6 cm. Find the height of the cylinder.
Solution:
Radius of the sphere (r1) = 4.2 cm
∴ Volume of the sphere = $$\frac{4}{3}$$ πr13
= $$\frac{4}{3} \times \frac{22}{7} \times \frac{42}{10} \times \frac{42}{10} \times \frac{42}{10} \mathrm{cm}^{3}$$
Radius of the cylinder (r2) = 6 cm
Let h be the height of the cylinder.
∴ Volume of the cylinder = πr2h
= $$\frac{22}{7}$$ × 6 × 6 × h cm3
Since volume of the metallic sphere = Volume of the cylinder

Hence, the height of the cylinder is 2.744 cm

Question 2.
Metallic spheres of radii 6 cm, 8 cm and 10 cm, respectively, are melted to form a single solid sphere. Find the radius of the resulting sphere.
Solution:
Radii of the given spheres are
r1 = 6 cm, r2 = 8 cm and r3 = 10 cm
⇒ Volume of the given spheres are

= $$\frac{4}{3} \times \frac{22}{7}$$ × [1728] cm3
Let the radius of the new big sphere be R. Volume of the new sphere
= $$\frac{4}{3}$$ × π × R3 = $$\frac{4}{3} \times \frac{22}{7}$$ × R3
Since, the two volumes must be equal.
∴ $$\frac{4}{3} \times \frac{22}{7} \times R^{3}=\frac{4}{3} \times \frac{22}{7} \times 1728$$
⇒ R3 = 1728 ⇒ R = 12 cm
Thus, the required radius of the resulting sphere is 12 cm.

Question 3.
A 20 m deep well with diameter 7 m is dug and the earth from digging is evenly spread out to form a platform 22 m by 14 m. Find the height of the platform.
Solution:
Diameter of the cylindrical well = 7 m
⇒ Radius of the cylindrical well (r) = $$\frac{7}{2}$$ m
Depth of the well (h) = 20 m
∴ Volume = πr2h = $$\frac{22}{7} \times \frac{7}{2} \times \frac{7}{2}$$ × 20 m3
= 22 × 7 × 5 m3
⇒ Volume of the earth taken out = 22 × 7 × 5 m3
Now this earth is spread out to form a cuboidal platform having length = 22 m, breadth = 14 m
Let h be the height of the platform.
∴ Volume of the platform = 22 × 14 × h m3
Since, the two volumes must be equal
∴ 22 × 14 × h = 22 × 7 × 5
Thus, the required height of the platform is 2.5 m.

Question 4.
A well of diameter 3 m is dug 14m deep. The earth taken out of it has been spread evenly all around it in shape of a circular ring of width 4 m to form an embankment. Find the height of the embankment.
Solution:
Diameter of cylindrical well = 3 m
⇒ Radius of the cylindrical well = $$\frac{3}{2}$$ m = 1.5 m
Depth of well (h) = 14 m
∴ Volume of cylindrical well

Let the height of the embankment = H m.
Internal radius of the embankment (r) = 1.5 m.
External radius of the embankment (R)
= (4 + 1.5) m = 5.5 m.
∴ Volume of the embankment
= πR2H – πr2H = πH [R2 – r2]
= πH (R + r) (R – r)
= $$\frac{22}{7}$$ × H (5.5 + 1.5)(5.5 – 1.5)
= $$\frac{22}{7}$$ × H × 7 × 4m3
Since, Volume of the embankment=Volume of the cylindrical well
⇒ $$\frac{22}{7}$$ × H × 7 × 4 = 99
⇒ H = 99 × $$\frac{7}{22} \times \frac{1}{7} \times \frac{1}{4} m=\frac{9}{8} m$$ = 1.125 m
So, the required height of the embankment = 1.125 m.

Question 5.
A container shaped like a right circular cylinder having diameter 12 cm and height 15 cm is full of ice cream. The ice cream is to be filled into cones of height 12 cm and 6. diameter 6 cm, having a hemispherical shape on the top. Find the number of such cones which can be filled with ice cream.
Solution:
For the circular cylinder:

Diameter = 12 cm
⇒ Radius (r) = $$\frac{12}{2}$$ = 6cm and height (h) = 15 cm
∴ Volume of circular cylinder
= πr2h = $$\frac{12}{2}$$ × 6 × 6 × 15 cm3
For conical and hemispherical part of icecream :
Diameter = 6 cm ⇒ radius (R) = 3 cm
Height of conical part (H) = 12 cm

Volume of ice cream cone = (Volume of the conical part) + (Volume of the hemispherical part)

Thus, the required number of cones is 10.

Question 6.
How many silver coins, 1.75 cm in diameter and of thickness 2 mm, must be melted to form a cuboid of dimensions 5.5 cm × 10 cm × 3.5 cm?
Solution:
For a circular coin:

Diameter = 1.75 cm
⇒ Radius (r) = $$\frac{175}{200}$$ cm
Thickness (h) = 2mm = $$\frac{2}{10}$$ cm
∴ Volume of one coin = πr2h = $$\frac{22}{7} \times\left(\frac{175}{200}\right)^{2} \times \frac{2}{10} \mathrm{cm}^{3}$$
For a cuboid:

Length (l) = 10 cm,
Breadth (b) = 5.5 cm
and height (h) = 3.5 cm
∴ Volume = l × b × h = 10 × $$\frac{55}{10} \times \frac{35}{10}$$ cm3

Thus, the required number of coins = 400.

Question 7.
A cylindrical bucket, 32 cm high and with radius of base 18 cm, is filled with sand. This bucket is emptied on the ground and a conical heap of sand is formed. If the height of the conical heap is 24 cm, find the radius and slant height of the heap.
Solution:
For the cylindrical bucket:
Radius (r) = 18 cm and height (h) = 32 cm
Volume of cylindrical bucket = πr2h
= $$\frac{22}{7}$$ × (18)2 × 32 cm3
⇒ Volume of the sand = ($$\frac{22}{7}$$ × 18 × 18 × 32) cm3
For the conical heap:
Height (H) = 24 cm
Let radius of the base be R.
∴ Volume of conical heap

Thus, the required radius = 36 cm and slant height = $$12 \sqrt{13}$$ cm.

Question 8.
Water in a canal, 6 m wide and 1.5 m deep, is flowing with a speed of 10 km/h. How much area will it irrigate in 30 minutes, if 8 cm of standing water is needed?
Solution:
Width of the canal = 6 m,
Depth of the canal = 1.5 m
Length of the water column in 1 hr = 10 km
∴ Length of the water column in 30 minutes
(i.e., $$\frac{1}{2}$$hr) = $$\frac{10}{2}$$ km = 5 km = 5000 m
∴ Volume of water flown in $$\frac{1}{2}$$ hr
= 6 × 1.5 × 5000 m3 = 6 × $$\frac{15}{10}$$ × 5000 m3
= 45000 m3
Since, the above amount (volume) of water is spread in the form of a cuboid of height
8 cm (= $$\frac{8}{100}$$ m)
Let the area of the cuboid = a
∴ Volume of the cuboid = Area × Height

= 562500 m2 = 56.25 hectares
Thus, the required area is 56.25 hectares.

Question 9.
A farmer connects a pipe of internal diameter 20 cm from a canal into a cylindrical tank in her field, which is 10 m in diameter and 2 m deep. If water flows through the pipe at the rate of 3 km/h, in how much time will the tank be filled?
Solution:
Diameter of the pipe = 20 cm
⇒ Radius of the pipe (r) = $$\frac{20}{2}$$ cm = 10 cm
Since, the water flows through the pipe at 3 km/hr.
∴ Length of water column per hour(h) = 3 km
= 3 × 1000 m = 3000 × 100 cm = 300000 cm.
Length of water column per hour(h) = 3 km
Volume of water flown in one hour = πr2h
= π × 102 × 300000 cm3 = π × 30000000 cm2
Now, for the cylindrical tank :
Diameter = 10 m
⇒ Radius (R) = $$\frac{10}{2}$$ m = 5 × 100 cm = 500 cm
Height (H) = 2 m = 2 × 100 cm = 200 cm
∴ Volume of the cylindrical tank = πR2H
= π × (500)2 × 200 cm3
Now, time required to fill the tank

## MP Board Class 10th Maths Solutions Chapter 15 Probability Ex 15.1

In this article, we will share MP Board Class 10th Maths Book Solutions Chapter 15 Probability Ex 15.1 Pdf, These solutions are solved subject experts from the latest edition books.

## MP Board Class 10th Maths Solutions Chapter 15 Probability Ex 15.1

Question 1.
Complete the following statements:
(i) Probability of an event E + Probability of the event ‘not E’ = _________
(ii) The probability of an event that cannot happen is ______.Such an event is called _________.
(iii) The probability of an event that is certain to happen is ______ Such an event is called ______
(iv) The sum of the probabilities of all the elementary events of an experiment is ______.
(v) The probability of an event is greater than or equal to _______ and less than or equal to ______.
Solution:
(i) 1 : Probability of an event E + Probability of the event ‘not E’ = 1.
(ii) 0, impossible: The probability of an event that cannot happen is 0. Such an event is called impossible event.
(iii) 1, certain: The probability of an event that is certain to happen is 1. Such an event is called a sure or certain event.
(iv) 1: The sum of the probabilities of all the elementary events of an experiment is 1.
(v) 0, 1: The probability of an event is greater than or equal to 0 and less than or equal to 1.

Question 2.
Which of the following experiments have equally likely outcomes? Explain.
(i) A driver attempts to start a car. The car starts or does not start.
(ii) A player attempts to shoot a basketball. She/he shoots or misses the shot.
(iii) A trial is made to answer a true-false question. The answer is right or wrong.
(iv) A baby is born. It is a boy or a girl.
Solution:
(i) It depends on various factors such as whether the car will start or not. So, the probability of car will start does not equal to the probability of car will not start.
∴ The outcomes are not equally likely.
(ii) It depends on the player’s ability. So, probability that the player shot the ball is not the same as the probability that the player misses the shot.
(iii) The outcomes are equally likely as the probability of answer either right or wrong is $$\frac{1}{2}$$
(iv) The outcomes are equally likely as the probability of ‘newly born baby to be either bay or girls’ is $$\frac{1}{2}$$ .

Question 3.
Why is tossing a coin considered to be a fair way of deciding which team should get the ball at the beginning of a football game?
Solution:
Since on tossing a coin, the outcomes ‘head’ and ‘tail’ are equally likely, the result of tossing a coin is completely unpredictable and so it is a fairway.

Question 4.
Which of the following cannot be the probability of an event?
(A) $$\frac{2}{3}$$
(B) -1.5
(C) 15%
(D) 0.7
Solution:
Since, the probability of an event cannot be negative.
∴ -1.5 cannot be the probability of an event.

Question 5.
If P(E) = 0.05, what is the probability of ‘not E’?
Solution:
∵ P(E) + P(not E) = 1
∴ 0.05 + P(not E) = 1 ⇒ P(not E) = 0.95
Thus, probability of ‘not E’ = 0.95.

Question 6.
A bag contains lemon flavoured candies only. Malini takes out one candy without looking into the bag. What is the probability that she takes out
(i) an orange flavoured candy?
(ii) a lemon flavoured candy?
Solution:
(i) Since there are only lemon flavoured candies in the bag.
∴ Taking out orange flavoured candy is not possible.
⇒ Probability of taking out an orange flavoured candy = 0.

(ii) Probability of taking out a lemon flavoured candy = 1.

Question 7.
It is given that in a group of 3 students, the probability of 2 students not having the same birthday is 0.992. What is the probability that the 2 students have the same birthday?
Solution:
Let the probability of 2 students having same birthday = P(SB)
And the probability of 2 students not having the same birthday = P(NSB)
∴ P(SB) + P(NSB) = 1
⇒ P(SB) + 0.992 = 1 ⇒ P(SB) = 1 – 0.992 = 0.008

Question 8.
A bag contains 3 red balls and 5 black balls. A ball is drawn at random from the bag. What is the probability that the ball drawn is
(i) red?
(ii) not red?
Solution:
Total number of balls = 3 + 5 = 8
∴ umber of possible outcomes = 8
(i) ∵ There are 3 red balls.
∴ Number of favourable outcomes = 3
∴ P (red) = $$\frac{\text { Number of favourable outcomes }}{\text { Number of all possible outcomes }}$$
= $$\frac{3}{8}$$
(ii) Probability of the ball drawn which is not red = 1 – P(red) = $$1-\frac{3}{8}=\frac{8-3}{8}=\frac{5}{8}$$

Question 9.
A box contains 5 red marbles, 8 white marbles and 4 green marbles. One marble is taken out of the box at random. What is the probability that the marble taken out will be
(i) red?
(ii) white?
(iii) not green?
Solution:
Total number of marbles = 5 + 8 + 4 = 17
∴ Number of all possible outcomes = 17
(i) ∵ Number of red marbles = 5
∴ Number of favourable outcomes = 5
∴ Probability of red marbles, P(red) = $$\frac{\text { Number of favourable outcomes }}{\text { Number of all possible outcomes }}=\frac{5}{17}$$

(ii) Number of white marbles = 8
∴ Probability of white marbles, P(white) = $$\frac{\text { Number of favourable outcomes }}{\text { Number of all possible outcomes }}=\frac{8}{17}$$
_ Number of favourable outcomes _ 8 Number of all possible outcomes 17

(iii) Number of green marbles = 4 Number of marbles which are not green
= 17-4 = 13
i.e., Favourable outcomes = 13
∴ Probability of marbles ‘not green’, P(not greeen)
$$\frac{\text { Number of favourable outcomes }}{\text { Number of all possible outcomes }}=\frac{13}{17}$$

Question 10.
A piggy bank contains hundred 50p coins, fifty ₹ 1 coins, twenty ₹ 2 coins and ten ₹ 5 coins. If it is equally likely that one of the coins will fall out when the bank is turned upside down, what is the probability that the coin
(i) will be a 50p coin?
(ii) will not be a ₹ 5 coin?
Solution:
Number of coins 50 p = 100, ₹ 1 = 50 ₹ 2 = 20, ₹ 5 = 10
Total number of coins = 100 + 50 + 20 +10 = 180
∴ Total possible outcomes = 180

(i) For a 50 p coin:
Favourable outcomes = 100

(ii) For not a ₹ 5 coin:
Y Number of ₹ 5 coins = 10
∴ Number of ‘not ₹ 5’ coins = 180 – 10 = 170
⇒ Favourable outcomes = 170

Question 11.
Gopi buys a fish from a shop for his aquarium. The shopkeeper takes out one fish at random from a tank containing 5 male fish and 8 female fish. What is the probability that the fish taken out is a male fish?
Solution:
Number of male fishes = 5
Number of female fishes = 8
∴ Total number of fishes = 5 + 8 = 13
⇒ Total number of outcomes = 13
For a male fish:
Number of favourable outcomes = 5

Question 12.
A game of chance consists of spinning an arrow which comes to rest pointing at one of the numbers 1, 2, 3, 4, 5, 6, 7, 8 (see figure), and these are equally likely outcomes. What is the probability that it will point at
(i) 8?
(ii) an odd number?
(iii) a number greater than 2?
(iv) a number less than 9?

Solution:
Total number marked = 8
∴ Total number of possible outcomes = 8
(i) When pointer points at 8:
Number of favourable outcomes = 1

(ii) When pointer points at an odd number:
∵ Odd numbers are 1, 3, 5 and 7
∴ Total odd numbers from 1 to 8 = 4
⇒ Number of favourable outcomes = 4

(iii) When pointer points at a number greater than 2:
∵ The numbers 3, 4, 5, 6, 7 and 8 are greater than 2
∴ Total numbers greater than 2 = 6
⇒ Number of favourable outcomes = 6

(iv) When pointer points at a number less than 9:
∵ The numbers 1, 2, 3, 4, 5, 6, 7 and 8 are less than 9.
∴ Total numbers less than 9 = 8
∴ Number of favourable outcomes = 8

Question 13.
A die is thrown once. Find the probability of getting:
(i) a prime number;
(ii) a number lying between 2 and 6;
(iii) an odd number.
Solution:
Since, numbers on a die are 1, 2, 3, 4, 5 and 6.
∴ Total number of possible outcomes = 6
(i) Since 2, 3 and 5 are prime number.
∴ Favourable outcomes = 3

(ii) Since the numbers between 2 and 6 are 3, 4 and 5
∴ Favourable outcomes = 3

(iii) Since 1, 3 and 5 are odd numbers.
⇒ Favourable outcomes = 3

Question 14.
One card is drawn from a well-shuffled deck of 52 cards. Find the probability of getting
(i) a king of red colour
(ii) a face card
(iii) a red face card
(iv) the jack of hearts
(vi) the queen of diamonds
Solution:
Number of cards in deck = 52
∴ Total number of possible outcomes = 52
(i) ∵ Number of red colour kings = 2
[∵ King of diamond and heart is red]
Number of favourable outcomes = 2

(ii) For a face card:
∵ 4 kings, 4 queens and 4 jacks are face cards
∴ Number of face cards = 12
⇒ Number of favourable outcomes = 12

(iii) Since, cards of diamond and heart are red
∴ There are 2 kings, 2 queens, 2 jacks i.e., 6 cards are red face cards.
∴ Number of favorable outcomes = 6

(iv) Since, there is only 1 jack of hearts.
∴ Number of favourable outcomes = 1

(v) There are 13 spades in a pack of 52 cards.
∴ Number of favourable outcomes = 13

(vi) ∵ There is only one queen of diamond.
∴ Number of favourable outcomes = 1

Question 15.
Five cards-the ten, jack, queen, king and ace of diamonds, are well-shuffled with their face downwards. One card is then picked up at random.
(i) What is the probability that the card is the queen?
(ii) If the queen is drawn and put aside, what is the probability that the second card picked up is (a) an ace? (b) a queen?
Solution:
We have five cards.
∴ Total number of possible outcomes = 5
(i) ∵ Number of queen = 1
∴ Number of favourable outcomes = 1

(ii) The queen is drawn and put aside.
∴ Only 5 – 1 = 4 cards are left.
∴ Total number of possible outcomes = 4
(a) ∵ There is only one ace.
∴ Number of favourable outcomes = 1

(b) Since, the only queen has been put aside already.
∴ Number of favourable outcomes = 0

Question 16.
12 defective pens are accidentally mixed with 132 good ones. It is not possible to just look at a pen and tell whether or not it is defective. One pen is taken out at random from this lot. Determine the probability that the pen taken out is a good one.
Solution:
We have number of good pens = 132 and number of defective pens = 12
∴ Total number of pens = 132 + 12 = 144 = Total possible outcomes
There are 132 good pens.
∴ Number of favourable outcomes = 132

Question 17.
(i) A lot of 20 bulbs contain 4 defective ones. One bulb is drawn at random from the lot. What is the probability that this bulb is defective?
(ii) Suppose the bulb drawn in (i) is not defective and is not replaced. Now one bulb is drawn at random from the rest. What is the probability that this bulb is not defective?
Solution:
Since, there are 20 bulbs in the lot.
Total number of possible outcomes = 20
(i) ∵ Number of defective bulbs = 4
∴ Favourable outcomes = 4

(ii) ∵ The bulb drawn above is not included in the lot.
∴ Number of remaining bulbs = 20 – 1 = 19.
⇒ Total number of possible outcomes = 19.
∵ Number of bulbs which are not defective = 19 – 4 = 15
⇒ Number of favourable outcomes = 15

Question 18.
A box contains 90 discs which are numbered from 1 to 90. If one disc is drawn at random from the box, find the probability that it bears
(i) a two-digit number
(ii) a perfect square number
(iii) a number divisible by 5.
Solution:
We have total number of discs = 90
∴ Total number of possible outcomes = 90
(i) Since the two-digit numbers are 10, 11, 12, ………, 90.
∴ Number of two-digit numbers = 90 – 9 = 81
∴ Number of favourable outcomes = 81

(ii) Perfect square from 1 to 90 are 1, 4, 9, 16, 25, 36, 49, 64 and 81.
∴ Number of perfect squares = 9
∴ Number of favourable outcomes = 9

(iii) Numbers divisible by 5 from 1 to 90 are 5, 10,15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90
i. e., There are 18 numbers from (1 to 90) which are divisible by 5.
∴ Numbers of favourable outcomes = 18

Question 19.
A child has a die whose six faces show the letters as given below:

The die is thrown once. What is the probability of getting (i) A? (ii) D?
Solution:
Since there are six faces of the given die and these faces are marked with letters

∴ Total number of letters = 6
∴ Total number of possible outcomes = 6
(i) ∵ Number of faces having the letter A = 2
∴ Number of favourable outcomes = 2

(ii) ∵ Number of faces having the letter D = 1
∴ Number of favourable outcomes = 1

Question 20.
20. Suppose you drop a die at random on the rectangular region shown in figure. What is the probability that it will land inside the circle with diameter 1 m?

Solution:
Here, area of the rectangle = 3m × 2m = 6 m2
And, the area of the circle = πr2

Question 21.
A lot consists of 144 ball pens of which 20 are defective and the others are good. Nuri will buy a pen if it is good, but will not buy if it is defective. The shopkeeper draws one pen at random and gives it to her. What is the probability that
(i) She will buy it? (ii) She will not buy it?
Solution:
Total number of ball pens = 144
⇒ Total number of possible outcomes = 144
(i) Since there are 20 defective pens.
∴ Number of good pens = 144 – 20 = 124
⇒ Number of favourable outcomes = 124

(ii) Probability that Nuri will not buy it = 1 – [Probability that she will buy it]
= $$1-\frac{31}{36}=\frac{36-31}{36}=\frac{5}{36}$$

Question 22.
Two dice, one blue and one grey, are thrown at the same time. Write down all the possible outcomes. An event is defined as the sum of the two numbers appearing on the top of the dice.
(i) Complete the following table

(ii) A student argues that’there are 11 possible outcomes 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12. Therefore, each of them has a probability $$\frac{1}{11}$$ Do you agree with this argument? Justify your answer.
Solution:
∵ The two dice are thrown together.
∴ Following are the possible outcomes :
(1, 1) ; (1, 2); (1, 3); (1, 4); (1, 5); (1, 6).
(2, 1) ; (2, 2); (2, 3); (2, 4); (2, 5); (2, 6).
(3, 1); (3, 2); (3, 3); (3, 4); (3, 5); (3, 6).
(4, 1) ; (4, 2); (4, 3); (4, 4); (4, 5); (4, 6).
(5, 1) ; (5, 2); (5, 3); (5, 4); (5, 5); (5, 6).
(6, 1) ; (6,.2); (6, 3); (6, 4); (6, 5); (6, 6).
∴ Total number of possible outcomes is 6 × 6 = 36
(i) (a) The sum on two dice is 3 for (1, 2) and (2, 1)
∴ Number of favourable outcomes = 2
⇒ P(3) = $$\frac{2}{36}$$

(b) The sum on two dice is 4 for (1, 3), (2, 2) and (3, 1).
∴ Number of favourable outcomes = 3
⇒ P(4) = $$\frac{3}{36}$$

(c) The sum on two dice is 5 for (1, 4), (2, 3), (3, 2) and (4,1)
∴ Number of favourable outcomes = 4
⇒ P(5) = $$\frac{5}{36}$$

(d) The sum on two dice is 6 for (1, 5), (2, 4), (3, 3), (4, 2) and (5,1)
∴ Number of favourable outcomes = 5
⇒ P(6) = $$\frac{5}{36}$$

(e) The sum on two dice is 7 for (1, 6), (2, 5), (3, 4), (4, 3), (5, 2) and (6,1)
∴ Number of favourable outcomes = 6
⇒ P(7) = $$\frac{62}{36}$$

(f) The sum on two dice is 9 for (3, 6), (4, 5), (5, 4) and (6, 3)
∴ Number of favourable outcomes = 4
⇒ P(9) = $$\frac{4}{36}$$

(g) The sum on two dice is 10 for (4, 6), (5, 5), (6,4)
∴ Number of favourable outcomes = 3
⇒ P(10) = $$\frac{3}{36}$$

(h) The sum on two dice is 11 for (5, 6) and (6,5)
∴ Number of favourable outcomes = 2
⇒ P(11) = $$\frac{2}{36}$$

Thus, the complete table is as follows:

(ii) No. The number of all possible outcomes is 36 not 11.
∴ The argument is not correct.

Question 23.
A game consists of tossing a one rupee coin 3 times and noting its outcome each time. Hanif wins if all the tosses give the same result i.e., three heads or three tails, and loses otherwise. Calculate the probability that Hanif will lose the game.
Solution:
Let T denotes the tail and H denotes the head.
∴ All the possible outcomes are:
{H H H, H H T, H T T, T T T, T T H, T H T, T H H, H T H)
∴ Number of all possible outcomes = 8
Let the event that Hanif will lose the game denoted by E.
∴ Favourable events are: {HHT, HTH, THH, THT, TTH, HTT}
⇒ Number of favourable outcomes = 6
∴ P(E) = $$\frac{6}{8}=\frac{3}{4}$$

Question 24.
A die is thrown twice. What is the probability that
(i) 5 will not come up either time?
(ii) 5 will come up at least once?
[Hint: Throwing a die twice and throwing two dice simultaneously are treated as the same experiment]
Solution:
Since, throwing a die twice or throwing two dice simultaneously is the same.
∴ All possible outcomes are:
(1, 1); (1, 2); (1, 3); (1, 4); (1, 5); (1, 6).
(2, 1); (2, 2); (2, 3); (2, 4); (2, 5); (2, 6).
(3, 1) ; (3, 2); (3, 3); (3, 4); (3, 5); (3, 6).
(4, 1); (4, 2); (4, 3); (4, 4); (4, 5); (4, 6).
(5, 1) ; (5, 2); (5, 3); (5, 4); (5, 5); (5, 6).
(6, 1) ; (6, 2); (6, 3); (6, 4); (6, 5); (6, 6).
∴ All possible outcomes = 36
(i) Let E be the event that 5 does not come up either time.
∴ Numebr of favourable outcomes = [36 – (5 + 6)] = 25
∴ P(E) = $$\frac{25}{36}$$
(ii) Let N be the event that 5 will come up at least once, then number of favourable outcomes = 5 + 6 = 11
∴ P(N) = $$\frac{11}{36}$$

Question 25.
Which of the following arguments are correct and which are not correct? Give reasons for your answer.
(i) If two coins are tossed simultaneously there are three possible outcomes – two heads, two tails or one of each. Therefore, for each of these outcomes, the probability is $$\frac{1}{3}$$.
(ii) If a die is thrown, there are two possible outcomes – an odd number or an even number. Therefore, the probability of getting an odd number is $$\frac{1}{3}$$
Solution:
(i) Given argument is not correct. Because, if two coins are tossed simultaneously then four outcomes are possible (HH, HT, TH, TT). So total outcomes is 4.
∴ The required probability = $$\frac{1}{4}$$.
(ii) Given argument is correct.
Since, total numebr of possible outcomes = 6
Odd numbers = 3 and even numbers = 3
So, favourable outcomes = 3 (in both the cases even or odd).
∴ Probability = $$\frac{3}{6}=\frac{1}{2}$$

## MP Board Class 10th Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4

In this article, we will share MP Board Class 10th Maths Book Solutions Chapter 13 Surface Areas and Volumes Ex 13.4 Pdf, These solutions are solved subject experts from the latest edition books.

## MP Board Class 10th Maths Solutions Chapter 13 Surface Areas and Volumes Ex 13.4

Use π = $$\frac{22}{7}$$, unless stated otherwise.

Question 1.
A drinking glass is in the shape of a frustum of a cone of height 14 cm. The diameters of its two circular ends are 4 cm and 2 cm. Find the capacity of the glass.
Solution:
We have,

d1 = 4 cm
∴ r1 = $$\frac{d_{1}}{2}$$ = 2 cm
and d2 = 2 cm
r2 = $$\frac{d_{2}}{2}$$ = 1 cm
and h = 14 cm
Volume of the glass

Question 2.
The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular ends are 18 cm and 6 cm. Find the curved surface area of the frustum.
Solution:
We have,
Slant height (l) = 4 cm
Circumference of one end = 2πr1 = 18 cm
and Circumference of other end = 2πr2 = 6 cm

⇒ πr1 = $$\frac{18}{2}$$ = 9 cm
and πr2 = $$\frac{6}{2}$$ = 3 cm
∴ Curved surface area of the frustum of the cone
= π(r1 + r2) l = (πr1 + πr2) l = (9 + 3 ) × 4 cm2
= 12 × 4 cm2 = 48 cm2.

Question 3.
A fez, the cap used by the Turks, is shaped like the frustum of a cone (see figure). If its radius on the open side is 10 cm, radius at the upper base is 4 cm and its slant height is 15 cm, find the area of material used for making it.

Solution:
Here, the radius of the open side (r1) = 10 cm
The radius of the upper base (r2) = 4 cm
Slant height (l) = 15 cm
∴ Area of the material required = [Curved surface area of the frustum] + [Area of the top end]
= π(r1 + r2)l + πr22

Question 4.
A container, opened from the top and made up of a metal sheet, is in the form of a frustum of a cone of height 16 cm with radii of its lower and upper ends as 8 cm and 20 cm, respectively. Find the cost of the milk which can completely fill the container, at the rate of ₹ 20 per litre. Also find the cost of metal sheet used to make the container, if it costs ₹ 8 per 100 cm2. (Take π = 3.14)
Solution:
We have, r1 = 20 cm, r2 = 8 cm and h = 16 cm

Area of the bottom = πr22
= ($$\frac{314}{100}$$ × 8 × 8) cm2 = 200.96 cm2
∴ Total area of metal required
= 1758.4 cm2 + 200.96 cm2 = 1959.36 cm2
Cost of metal required for 100 cm2 = ₹ 8
∴ Cost of metal required for 1959.36 cm2
= ₹ $$\frac{8}{100}$$ × 1959.36 = ₹ 156.75

Question 5.
A metallic right circular cone 20 cm high and whose vertical angle is 60° is cut into two parts at the middle of its height by a plane parallel to its base. If the frustum so obtained be drawn into a wire of diameter $$\frac{1}{16}$$ find the length of the wire
Solution:
Let us consider the frustum DECB of the metallic cone ABC

Thus, the required length of the wire = 7964.44 m

## MP Board Class 10th Maths Solutions Chapter 10 Circles Ex 10.2

In this article, we will share MP Board Class 10th Maths Book Solutions Chapter 10 Circles Ex 10.2 Pdf, These solutions are solved subject experts from the latest edition books.

## MP Board Class 10th Maths Solutions Chapter 10 Circles Ex 10.2

In questions 1 to 3, choose the correct option and give justification.

Question 1.
From a point Q, the length of the tangent to a circle is 24 cm and the distance of Q from the centre is 25 cm. The radius of the circle is
(A) 7 cm
(B) 12 cm
(C) 15 cm
(D) 24.5 cm
Solution:
(A): ∵ QT is a tangent to the circle at T and OT is radius

∴ OT⊥QT
Also, OQ = 25 cm and QT = 24 cm
∴ Using Pythagoras theorem, we get
OQ2 = QT2 + OT2
⇒ OT2 = OQ2 – QT2 = 252 – 242 = 49
⇒ OT = 7
Thus, the required radius is 7 cm.

Question 2.
In figure, if TP and TQ are the two tangents to a circle with centre 0 so that ∠POQ =110°, then ∠PTQ is equal to
(A) 60°
(B) 70°
(C) 80°
(D) 90°

Solution:
(B): TQ and TP are tangents to a circle with centre O and ∠POQ = 110°
∴ OP⊥PT and OQ⊥QT
⇒ ∠OPT = 90° and ∠OQT = 90°
Now, in the quadrilateral TPOQ, we get
∠PTQ + 90° + 110° + 90° = 360° [Angle sum property of a quadrilateral]
⇒ ∠PTQ + 290° = 360°
⇒ ∠PTQ = 360° – 290° = 70°

Question 3.
If tangents PA and PB from a point P to a circle with centre O are inclined to each other at angle of 80°, then ∠POA is equal to
(A) 50°
(B) 60°
(C) 70°
(D) 80°
Solution:
(A) : Since, O is the centre of the circle and two tangents from P to the circle are PA and PB.
∴ OA⊥AP and OB⊥BP
⇒ ∠OAP = ∠OBP = 90°

Now, in quadrilateral PAOB, we have
∠BPA + ∠PAO + ∠AOB + ∠OBP = 360°
⇒ 80° + 90° + ∠AOB + 90° = 360°
⇒ 260° + ∠AOB = 360°
⇒ ∠AOB = 360° – 260° ⇒ ∠AOB = 100°
In right ∆OAP and right ∆OBP, we have
OP = OP [Common]
∠OAP = ∠OBP [Each 90°]
OA = OB [Radii of the same circle]
∴ ∆OAP ≅ ∆OBP [By RHS congruency]
⇒ ∠POA = ∠POB [By CPCT]
∴ ∠POA = $$\frac{1}{2}$$ ∠AOB = $$\frac{1}{2}$$ × 100° = 50°

Question 4.
Prove that the tangents drawn at the ends of a diameter of a circle are parallel.
Solution:
In the figure, PQ is diameter of the given circle and O is its centre.
Let tangents AB and CD be drawn at the end points of the diameter PQ.
Since, the tangents at a point to a circle is perpendicular to the radius through the point.

∴ PQ⊥AB
⇒ ∠APQ = 90°
And PQ⊥CD
⇒ ∠PQD = 90° ⇒ ∠APQ = ∠PQD
But they form a pair of alternate angles.
∴ AB || CD
Hence, the two tangents are parallel.

Question 5.
Prove that the perpendicular at the point of contact to the tangent to a circle passes through the centre.
Solution:
In the figure, the centre of the circle is O and tangent AB touches the circle at P. If possible, let PQ be perpendicular to AB such that it is not passing through O.
Join OP.
Since, tangent at a point to a circle is perpendicular to the radius through that point.

∴ OP⊥AB
⇒ ∠OPB = 90° ……….. (1)
But by construction, PQ⊥AB
⇒ ∠QPB = 90° ………….. (2)
From (1) and (2),
∠QPB = ∠OPB
which is possible only when O and Q coincide. Thus, the perpendicular at the point of contact to the tangent to a circle passes through the centre.

Question 6.
The length of a tangent from a point A at distance 5 cm from the centre of the circle is 4 cm. Find the radius of the circle.
Solution:
∵ The tangent to a circle is perpendicular to the radius through the point of contact.
∴ ∠OTA = 90°
Now, in the right ∆OTA, we have
OA2 = OT2 + AT2 [Pythagoras theorem]

⇒ OT2 = 52 – 42
⇒ OT2 = (5 – 4)(5 + 4)
⇒ OT2 = 1 × 9 = 9 = 32
⇒ OT = 3
Thus, the radius of the circle is 3 cm.

Question 7.
Two concentric circles are of radii 5 cm and 3 cm. Find the length of the chord of the larger circle which touches the smaller circle.
Solution:
In the figure, O is the common centre, of the given concentric circles.
AB is a chord of the bigger circle such that it is a tangent to the smaller circle at P.
Since, OP is the radius of the smaller circle.
∴ OP⊥AB ⇒ ∠APO = 90°
Also, radius perpendicular to a chord bisects the chord.

∴ OP bisects AB
⇒ AP = $$\frac{1}{2}$$ AB
Now, in right ∆APO,
OA2 = AP2 + OP2
⇒ 52 = AP2 + 32 ⇒ AP2 = 52 – 32
⇒ AP2 = 42 ⇒ AP = 4 cm
⇒ $$\frac{1}{2}$$ AB = 4 ⇒ AB = 2 × 4 = 8 cm
Hence, the required length of the chord AB is 8 cm.

Question 8.
A quadrilateral ABCD is drawn to circumscribe a circle (see figure).

Prove that AB + CD = AD + BC
Solution:
Since, the sides of quadrilateral ABCD, i.e., AB, BC, CD and DA touches the circle at P, Q, R and S respectively, and the lengths of two tangents to a circle from an external point are equal.
∴ AP = AS, BP = BQ,
DR = DS and CR = CQ
Adding them, we get
(AP + BP) + (CR + RD) = (BQ + QQ) + (DS + SA)
⇒ AB + CD = BC + DA

Question 9.
In figure, XY and X’Y’ are two parallel tangents to a circle with centre O and another tangent AB with point of contact C intersecting XY at A and X’Y’ at B.

Prove that ∠AOB = 90°.
Solution:
∵ The tangents drawn to a circle from an external point are equal.
∴ AP = AC ……… (1)
Join OC.
In ∆PAO and ∆CAO, we have
AO = AO [Common]
OP = OC [Radii of the same circle]
AP = AC [From (1)]
⇒ ∆PAO ≅ ∆CAO [SSS congruency]
∴ ∠PAO = ∠CAO
⇒ ∠PAC = 2∠CAO …………. (2)
Similarly, ∠CBQ = 2∠CBO ……………… (3)

Again, we know that sum of internal angles on the same side of a transversal is 180°.
∴ ∠PAC + ∠CBQ = 180°
2∠CAO + 2∠CBO = 180° [From (2) and (3)]
⇒ ∠CAO + ∠CBO = $$\frac{180^{\circ}}{2}$$ = 90° …………… (4)
Also, in ∆AOB,
∠BAO + ∠OBA + ∠AOB = 180° [Sum of angles of a triangle]
⇒ ∠CAO + ∠CBO + ∠AOB = 180°
⇒ 90° + ∠AOB = 180° [From (4)]
⇒ ∠AOB = 180° – 90°
⇒ ∠AOB = 90°

Question 10.
Prove that the angle between the two tangents drawn from an external point to a circle is supplementary to the angle subtended by the line-segment joining the points of contact at the centre.
Solution:
Let PA and PB be two tangents drawn from an external point P to a circle with centre O.

Now, in right ∆OAP and right ∆OBP, we have
PA = PB [Tangents to circle from an external point]
OA = OB [Radii of the same circle]
OP = OP [Common]
⇒ ∆OAP ≅ ∆OBP [By SSS congruency]
∴ ∠OPA = ∠OPB [By CPCT]
and ∠AOP = ∠BOP
⇒ ∠APB = 2∠OPA and ∠AOB = 2∠AOP
In right ∆OAP,
∠AOP + ∠OPA + ∠PAO = 180°
⇒ ∠AOP = 180° – 90° – ∠OPA
⇒ ∠AOP = 90° – ∠OPA
⇒ 2∠AOP = 180° – 2∠OPA
⇒ ∠AOB = 180° – ∠APB
⇒ ∠AOB + ∠APB = 180°

Question 11.
Prove that the parallelogram circumscribing a circle is a rhombus.
Solution:
We have ABCD, a parallelogram which circumscribes a circle (i.e., its sides touch the circle) with centre O.
Since, tangents to a circle from an external point are equal in length

∴ AP = AS
BP = BQ
CR = CQ
DR = DS
On adding, we get
(AP + BP) + (CR + DR) = (AS + DS) + (BQ + CQ)
⇒ AB + CD = AD + BC
But AB = CD [Opposite sides of parallelogram]
and BC = AD
∴ AB + CD = AD + BC ⇒ 2AB = 2BC
⇒ AB = BC
Similarly, AB = DA and DA = CD
Thus, AB = BC = CD = DA
Hence, ABCD is a rhombus.

Question 12.
A triangle ABC is drawn to circumscribe a circle of radius 4 cm such that the segments BD and DC into which BC is divided by the point of contact D are of lengths 8 cm and 6 cm respectively (see figure). Find the sides AB and AC.

Solution:
Here ∆ABC circumscribes the circle with centre O. Also, radius = 4 cm
Let AC and AB touches the circle at E and F, respectively and join OE and OF.
∵ The sides BC, CA and AB touches the circle at D, E and F respectively.
∴ BF = BD = 8 cm
[ ∵ Tangents to a circle from an external point are equal]
CD = CE = 6 cm
AF = AE = x cm (say)

∴ The sides of the ∆ABC are 14 cm, (x + 6) cm and (x + 8) cm
Perimeter of ∆ABC
= [14 + (x + 6) + (x + 8)] cm
= [14 + 6 + 8 + 2x] cm
= (28 + 2x) cm
⇒ Semi perimeter of ∆ABC,
s = $$\frac{1}{2}$$ [28 + 2x] cm = (14 + x) cm
∴ s – a = (14 + x) – (8 + x) = 6
s – b = (14 + x) – (14) = x
s – c = (14 + x) – (6 + x) = 8
where, a = AB, b = BC, c = AC

Squaring both sides, we get
(14 + x)2 = (14 + x)3x
⇒ 196 + x2 + 28x = 42x + 3x2
⇒ 2x2 + 14x – 196 = 0
⇒ x2 + 7x – 98 = 0
⇒ (x – 7)(x + 14) = 0
⇒ x – 7 = 0 or x + 14 = 0
⇒ x = 7 or x = -14
But x = -14 is rejected.
∴ x = 7
Thus, AB = 8 + 7 = 15 cm, BC = 8 + 6 = 14 cm and CA = 6 + 7 = 13 cm

Question 13.
Prove that opposite sides of a quadrilateral circumscribing a circle subtend supplementary angles at the centre of the circle.
Solution:
We have a circle with centre O. A quadrilateral ABCD is such that the sides AB, BC, CD and DA touches the circle at P, Q, R and S respectively.
Join OP, OQ, OR and OS.
We know that two tangents drawn from an external point to a circle subtend equal angles at the centre.

∴ ∠1 = ∠2
∠3 = ∠4
∠5 = ∠6 and ∠7 = ∠8
Also, the sum of all the angles around a point is 360°.
∴ ∠1 + ∠2 + ∠3 + ∠4 + ∠5 + ∠6 + ∠7 + ∠8 = 360°
∴ 2(∠1 + ∠8 + ∠5 + ∠4) = 360°
⇒ (∠1 + ∠8 + ∠5 + ∠4) = 180° …………. (1)
and 2(∠2 + ∠3 + ∠6 + ∠7) = 360°
⇒ (∠2 + ∠3 + ∠6 + ∠7) = 180° ……………. (2)
Since, ∠2 + ∠3 = ∠AOB, ∠6 + ∠7 = ∠COD, ∠1 + ∠8 = ∠AOD and ∠4 + ∠5 = ∠BOC
∴ From (1) and (2), we have
∠AOD + ∠BOC = 180°
and ∠AOB + ∠COD = 180°