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Air |Exercises solution | Class 7| Our Environment UPSC

 1. Answer the following questions.


(i) What is the atmosphere?

Answer:

  • Our earth is surrounded by a huge blanket of air is called the atmosphere.


(ii) Which two gases make the bulk of the atmosphere?

Answer:

  • Nitrogen( 78%) and Oxygen( 21%) are two major gases of the atmosphere.


(iii) Which gas creates the greenhouse effect in the atmosphere?

Answer:

Co2-Carbon dioxide gas creates a greenhouse effect in the atmosphere by trapping the temperature.


(iv) What is the weather?

Answer:

Weather is a short term atmospheric phenomenon of the atmosphere such as day to day and hour to hour atmospheric condition.


(v) Name three types of rainfall?

Answer:

The following are three types of rainfall.

  • Convection rainfall
  • Cyclonic rainfall
  • Orographic rainfall


(vi) What is air pressure?

Answer:

Air pressure can be defined as the pressure exerted by the weight of air on the earth's surface.


2. Tick the correct answer.


(i) Which of the following gases protects us from harmful sun rays?

(a) Carbon dioxide 

(b) Nitrogen

 (c) Ozone

Answer:

c) Ozone


(ii) The most important layer of the atmosphere is

(a) Troposphere 

(b) Thermosphere 

(c) Mesosphere

Answer:

a) Troposphere


(iii) Which of the following layers of the atmosphere is free from clouds?

(a) Troposphere
(b) Stratosphere

(c) Mesosphere

Answer:

b) Stratosphere


(iv) As we go up the layers of the atmosphere, the pressure

(a) Increases 

(b) Decreases 

(c) Remains the same

Answer:

b) Decrease


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

(a) Cloud 

(b) Rain 

(c) Snow

Answer:

b) Rain


3. Match the following.


(i) Trade Winds              (a) Incoming solar energy

(ii) Loo                             (b) Seasonal wind

(iii) Monsoon                 (c) Horizontal movement of Air

(iv) Wind                         (d) Layer of ozone gas

                                        (e) Permanent wind

                                         (f) Local wind

Answer:

(i) Trade Winds              (e) Permanent wind

(ii) Loo                           (f) Local wind 

(iii) Monsoon                 (b) Seasonal  wind 

(iv) Wind                        (c) Horizontal movement of Air

                            

                                    

4. Give reasons.


(i) Wet clothes take a longer time to dry on a humid day?

Answer:

Humid day slow down the evaporation process of wet cloth, that is why it takes a longer time to dry.

 

(ii) Amount of insolation decreases from the equator towards poles?

Answer:

The angle of sun rays gets decreases from the equator to the poles. Poles get very slanting sunray. Sun never rises much above the horizon while the Equator gets 90 degrees sun rays in the summer months. That is why insolation decrease from the equator towards the poles.



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