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Question : 71 of 150
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Solution:
The atmosphere around the earth:
- The atmosphere consists of different layers with varying density and temperature.
- The column of the atmosphere is divided into five different layers depending upon the temperature condition.
- They are troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
The troposphere
- It is the lowermost layer of the atmosphere.
- Its average height is 13 km and extends roughly to a height of 8 km near the poles and about 18 km at the equator.
- The thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents.
- This layer contains dust particles and water vapour.
- All changes in climate and weather take place in this layer.
- The temperature in this layer decreases at the rate of 1°C for every 165m of height.
- This is the most important layer for all biological activity.
- The zone separating the troposphere from the stratosphere is known as the tropopause.
- The air temperature at the tropopause is about minus 80 degrees celsius over the equator and about minus 45 degrees celsius over the poles.
- The temperature here is nearly constant, and hence, it is called the tropopause.
The stratosphere
- It is found above the tropopause and extends up to a height of 50 km.
- One important feature of the stratosphere is that it contains the ozone layer.
- This layer absorbs ultra-violet radiation and shields life on the earth from an intense, harmful form of energy.
The mesosphere
- It lies above the stratosphere, which extends up to a height of 80 km.
- In this layer, once again, the temperature starts decreasing with the increase in altitude and reaches up to minus 100°C at a height of 80 km.
- The upper limit of the mesosphere is known as the mesopause.
The thermosphere
- It is located between 80 and 400 km above the mesopause.
- It contains electrically charged particles known as ions, and hence, it is also known as the ionosphere.
- Radio waves transmitted from the earth are reflected back to the earth by this layer.
- The temperature here starts increasing with height.
The exosphere
- It is the uppermost layer of the atmosphere.
- This is the highest layer but very little is known about it.
- Whatever contents are there, these are extremely rarefied in this layer, and it gradually merges with the outer space.
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