Effects of Atmosphere on Living Beings — Social Science STD 7 — Question
Gujarat BoardEnglish MediumSTD 7Social ScienceEffects of Atmosphere on Living Beings4 Marks
Question
Explain the formation of atmosphere.
✓
Answer
The temperature of the atmosphere is not uniform at various altitude from the surface of the earth. On the basis of the changes in the temperature and the composition of gases, the atmosphere is divided into four zones: $(1)$ Troposphere $(2)$ Stratosphere $(3)$ Mesosphere and $(4)$ Thermosphere.
$(1)$ Troposphere : The first layer of the atmosphere starting from the surface of the carth is called "Troposphere'.
It extends up to an altitude of approximately $16 \ km$ on cquator.
12 km on temperate zones and 8 km on poles.
There are changes in the layers according to the seasons in troposphere. This layer allects the life (ccosystem) very much on the carth.
In this zone, atmospheric disturbances, noises, sound waves, formation of the air, lightning, clouds, rain, etc. occur.
The temperature decreases at the rate of about $6.5 ^\circ C$. per km of altitude in this zone.
The height at which the temperature stops decreasing that limit is called 'Tropopause'.
$(2)$ Stratosphere
This layer of the atmosphere up to a height of $50$ kilometres from the Tropopause. ,Temperature in this layer remains uniform.
That is why it is called 'stratosphere'. Movement of the air. storms, clouds, rain. seasons or snow do not occur here.
The air here is very thin and clear. So it is most favourable for flights.
Jet planes can fly faster with lesser obstruction. [Temperature stops increasing at the height of $50 km$ in this layer.
The height at which the temperature stops increasing is called as 'Tropopause' The layer situated at an altitude between 15 to 35 km of stratosphere is called 'Ozone layer'.
There is more proportion of ozone gas which absorbs the extremely hot ultra- violet sunrays. Ozone gas purifies the air. It is hygienic for human beings. When the asteroids pass through this layer, they are burnt and destroyed.
$(3)$ Mesosphere : The part of atmospheric zone extending up to an altitude of about $80 km$ above the stratosphere is called "Mesosphere'
$(4)$ Thermosphere : Starting from about 80 km above the mesosphere till the end of the atmosphere, the entire layer of the air is called "Thermosphere.
In this layer of the atmosphere, the air is extremely thin and hot.
The temperature increases as we go higher and higher in this layer. This is divided into two divisions : lonosphere and Exosphere.
The radio and television waves are reflected back from the lonosphere.
The transmission of television, radio broadcasting and the advantage of Internet are indebted to this layer.
The layer above the lonosphere is called 'Exosphere'.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.