Class 9 SST Understanding Society india and beyond Chapter 3 Atmosphere and Climate Excercise

Questions and activities

1. What is atmosphere? Explain its composition with the help of a pie diagram.

2. Draw a labelled diagram of the structure of atmosphere.

Which are the four main seasons of India? 3.

Why do you not feel the pressure of the atmosphere? 4.

5. In which layer of the atmosphere do aeroplanes fly and why?

6. Distinguish between the following:

a. The troposphere and stratosphere

b. The south-west monsoon and north-east monsoon

7. Do it yourself: Table 3.3 shows the average monthly temperatures and rainfall amounts for 10 representative stations. Study these figures on your own and convert them into 'temperature and rainfall' graphs. The visual representations will help you grasp their similarities and differences at a glance. One such graph (Fig. 3.14) is already prepared for you. See if you can arrive at some broad generalisations about our diverse climatic conditions.

7.1. Now look at Table 3.3 again. Re-arrange the 10 stations according to their distance from the equator.

7.2 Find out:

a. Two stations with the most extreme climate.

b. Two stations influenced by retreating monsoons.

c. The two hottest stations in the months of

(i) February

(ii) June

7.3. Now find out:

a. Why does Shillong experience more rainfall than Kolkata?

b. Why does Delhi receive more rainfall than Jodhpur?

Answers 

Here are concise answers to the questions:

1. What is the atmosphere? Explain its composition with the help of a pie diagram.

The atmosphere is the blanket of gases surrounding the Earth. It protects life by providing oxygen, regulating temperature, and blocking harmful solar radiation.

Composition of the Atmosphere:

Nitrogen (N₂) – 78%

Oxygen (O₂) – 21%

Argon – 0.93%

Carbon dioxide (CO₂) – 0.04%

Other gases – 0.03%

Pie Diagram (Percentages):

🟦 Nitrogen – 78%

🟩 Oxygen – 21%

🟨 Argon – 0.93%

🟥 Carbon dioxide & other gases – 0.07%

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2. Draw a labelled diagram of the structure of the atmosphere.

Exosphere

-------------------------

 Thermosphere

-------------------------

  Mesosphere

-------------------------

  Stratosphere

 (Ozone Layer)

-------------------------

 Troposphere

 (Weather occurs here)

-------------------------

   Earth

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3. Which are the four main seasons of India?

1. Cold Weather Season (Winter) – December to February

2. Hot Weather Season (Summer) – March to May

3. South-West Monsoon (Rainy Season) – June to September

4. Retreating Monsoon (North-East Monsoon) – October to November

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4. Why do you not feel the pressure of the atmosphere?

We do not feel atmospheric pressure because the pressure inside our body balances the pressure exerted by the atmosphere.

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5. In which layer of the atmosphere do aeroplanes fly and why?

Aeroplanes usually fly in the lower Stratosphere because:

It has stable air.

There are fewer clouds and storms.

Air turbulence is less, making flights smoother.

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6. Distinguish between the following:

(a) Troposphere and Stratosphere

Troposphere Stratosphere

Lowest layer Above the troposphere

Weather occurs here Contains the ozone layer

Temperature decreases with height Temperature increases with height

About 8–18 km thick About 18–50 km thick

(b) South-West Monsoon and North-East Monsoon

South-West Monsoon North-East Monsoon

June to September October to November

Winds blow from sea to land Winds blow from land to sea

Brings most of India's rainfall Brings rainfall mainly to Tamil Nadu

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7. Activity

Prepare temperature-rainfall graphs using Table 3.3 from your textbook.

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7.1 Arrange the 10 stations according to their distance from the Equator.

Use the latitude values given in Table 3.3 and arrange them from south to north.

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7.2 Find out

(a) Two stations with the most extreme climate:

Delhi

Jodhpur

(b) Two stations influenced by retreating monsoons:

Chennai

Puducherry

(c) Two hottest stations:

February: Thiruvananthapuram and Chennai

June: Jodhpur and Delhi

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7.3 Find out

(a) Why does Shillong experience more rainfall than Kolkata?

Shillong receives heavier rainfall because moisture-laden monsoon winds are forced to rise over the hills, causing orographic rainfall.

(b) Why does Delhi receive more rainfall than Jodhpur?

Delhi receives more rainfall because it lies in the direct path of the South-West Monsoon, whereas Jodhpur is located in the drier Thar Desert region and receives less rainfall.