Monday, September 21, 2015

CBSE Class 7 - Our Environment - Ch 4- Air (NCERT Solution)

 Air

Atmosphere Composition
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Class 7 - Geography - NCERT Chapter 4 Solution


Q1: What is atmosphere?

Answer: The thick blanket of air (mixture of gases) around the earth is called atmosphere.


Q2: Which two gases make the bulk of the atmosphere?

Answer: Nitrogen and Oxygen


Q3: Which gas creates green house effect in the atmosphere?

Answer: Ozone, Carbon DiOxide.


Q4: What is weather?

Answer: The state or condition of atmosphere at a particular time and place is called weather.


Q5: Name three types of rainfall?

Answer: Orographic, convectional and cyclonic rain.




Q6: What is air pressure?

Answer: The pressure exerted due to the weight of air on the earth's surface is called air pressure.


Q7(MCQ): Which of the following gases protects us from harmful sun rays?

(a) Carbon dioxide
(b) Nitrogen
(c) Ozone


Answer:  (c) Ozone

Q8(MCQ): The most important layer of the atmosphere is

(a) Troposphere
(b) Thermosphere
(c) Mesosphere


Answer:  (a) Troposhpere

Q9(MCQ): Which of the following layers of the atmosphere is free from clouds?

(a) Troposphere
(b) Stratosphere
(c) Mesosphere

Answer: (b) Stratosphere


Q10(MCQ): As we go up the layers of the atmosphere, the pressure

(a) Increases
(b) Decreases
(c) Remains the same

Answer: (c) decreases


Q11(MCQ): When precipitation comes down to the earth in the liquid form, it is called

(a) Cloud
(b) Rain
(c) Snow

Answer: (b) Rain


Q12: Match the following.
   (i) Trade Winds         (a) Seasonal wind
   (ii) Loo                (b) Horizontal movement of Air
   (iii) Monsoon           (c) Permanent wind
   (iv) Wind               (d) Local wind


Answer: (i) - (c), (ii) - (d), (3) - (a), (4) - (b)


Q13: Give reasons.
(i) Wet clothes take longer time to dry on a humid day?
(ii) Amount of insolation decreases from equator towards poles?


Answer:
(i) On a humid day air is saturated with water vapours, therefore wet clothes take longer time to dry.

(ii) Since sun rays fall vertically on the eauator while on poles rays fall slanting, thus amount of insolation decreases from equator towards poles.


Q14: List three importance of atmosphere.

Answer: Importance of atmosphere

1. The atmosphere prevents the Earth from becoming too hot during the day or too cold during the night.
2. It prevents the harmful ultra-violet rays of the Sun from reaching the Earth’s surface.
3. The atmosphere is the source of life-supporting gases such as Oxygen, Nitrogen, and Carbon dioxide.

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