NCERT Solution Class 7 Geography
CBSE Guide Class 7
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Air
Air - NCERT Guide Geography Class 7
Q1: Answer the following questions.
- What is Atmosphere?
- Which two gases make the bulk of atmosphere?
- Which gas creates Green House effect in atmosphere?
- What is Weather?
- Name three types of Rainfall.
- What is Air Pressure?
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Ans:
- Atmosphere is the blanket of air which surrounds the earth from all sides.
- Two gases which make the bulk of atmosphere are nitrogen and oxygen.
- Carbon dioxide creates Green House effect in atmosphere.
- ‘Weather’ is the sum total of the atmospheric conditions of a specific place at a specific time regarding the temperature, humidity, air pressure, clouds, winds etc.
- The three types of rainfall are - Conventional rainfall, Orographic rainfall and Cyclonic or Frontal rainfall.
- Air has weight and so, exerts pressure. Hence, air pressure is the impact which occurs due to air weight.
Q2: Tick the correct answer.
(i) Which of the following gases protects us from harmful sun rays?
- Carbon Dioxide
- Nitrogen
- Ozone
(ii) The most important layer of atmosphere is
- Troposphere
- Thermosphere
- Mesosphere
(iii) Which of the following layers of atmosphere is free from clouds?
- Troposphere
- Stratosphere
- Mesosphere
(iv) As we go up the layer of the atmosphere, the pressure
- Increases
- Decreases
- Remains same.
(v) When precipitation comes down to the earth in the liquid form, it is called -
- Cloud
- Rain
- Snow
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Ans:
(i) c. (ii) a. (iii) b. (iv) b. (v) b.
Q3: Match the items in column I with those in column II:
| Column I |
Column II |
- Trade winds
- Loo
- Monsoon
- Wind
|
- Seasonal wind
- Horizontal movement of air
- Permanent wind
- Local wind
|
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Q4:Give reasons:
- Wet clothes take longer time to dry on a humid day.
- Amount of insolation decreases from equator towards poles.
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Ans:
- On a humid day evaporation takes place at a much slower rate than a dry day. Therefore, evaporation from
a wet cloth is also slow. Hence, wet clothes take longer time to dry on a humid day.
- On equator insolation comes through vertical rays. Due to the vertical path it reacts upon less space and hence, felt more intensive on equator. From equator towards poles insolation comes through slanting rays. These slanting rays come on earth passing longer distance through atmosphere. More heat is consumed in the space and atmosphere. It is because of these reasons that the amount of insolation decreases from equator towards poles.
