Goa Board Class 7 Solutions for Geography – Air (English Medium)
Page No. 27:
Question 1:
Answer the following questions.
(i) What is atmosphere?
(ii) Which two gases make the bulk of the atmosphere?
(iii) Which gas creates green house effect in the atmosphere?
(iv) What is weather?
(v) Name three types of rainfall?
(vi) What is air pressure?
Solution :
(i) Earth is enveloped by a blanket of air. This envelopment/blanket is called ‘atmosphere’.
(ii) Oxygen and nitrogen constitute the bulk of the atmosphere.
(iii) Carbon dioxide creates the greenhouse effect in the atmosphere.
(iv)Weather is the collection of short-term changes in the atmosphere of the Earth. It is, in essence, the hour-to-hour, day-to-day condition of the atmosphere.
(v) Convectional rainfall, orographic rainfall and cyclonic rainfall are the three types of rainfall.
(vi) Air pressure is the pressure exerted by the weight of the air on the surface of the Earth.
Question 2:
Tick the correct answer.
(i) Which of the following gases protect us from the harmful sun rays?
(a) Carbon dioxide
(b) Nitrogen
(c) Ozone
(ii) The most important layer of the atmosphere is
(a) Troposphere
(b) Thermosphere
(c) Mesosphere
(iii) Which of the following layers of the atmosphere is free from clouds?
(a) Troposphere
(b) Stratosphere
(c) Mesosphere
(iv) As we go up the layers of the atmosphere, the pressure
(a) Increases
(b) Decreases
(c) Remains the same
(v) When precipitation comes down to the Earth in the liquid form, it is called
(a) Cloud
(b) Rain
(c) Snow
Solution :
(i) – (c) Ozone
(ii) – (a) Troposphere
(iii) – (b) Stratosphere
(iv) – (b) Decreases
(v) – (b) Rain
Question 3:
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 windc
Solution :
(i) – (c) Permanent wind
(ii) – (d) Local wind
(iii) – (a) Seasonal wind
(iv) – (b) Horizontal movement of air
Question 4:
Give reasons.
(i) Wet clothes take longer time to dry on a humid day?
(ii) Amount of insolation decreases from Equator towards Poles?
Solution :
(i) Humidity is the amount of moisture or water vapour present in air at any particular point of time. On a humid day, the level of water vapour in the air is more and as the air gets warmer, this level too increases. As a result, wet clothes take longer time to dry on a humid day.
(ii) Insolation is in fact the incoming solar radiations that are intercepted by the Earth. There is a tilt in the axis of the Earth. As a result of this tilt, the sunlight, and by extension, the incoming radiations, cover a larger area at the Equator than at the Poles.