Describe the structure of the atmosphere with the help of a diagram.
The atmosphere is divided into five layers beginning from the surface of the Earth. These are:
- It is the most important layer of the atmosphere and extends up to 13 km above the surface of the Earth.
- Oxygen required for respiration and survival of life exists in this layer of the Earth.
- The temperature decreases in this layer with an increase in the height.
- All the weather phenomena like rainfall, hail and fog occur in this layer as clouds are formed in this layer.
- The upper limit of the troposphere is known as the tropopause. Temperatures may be as low as -58°C at this level.
- This layer of atmosphere lies above the troposphere and extends up to a height of 50 km.
- Airplanes fly in this layer, as this layer is free from clouds and other weather phenomena. This layer is also free from the water vapour and dust particles.
- Stratosphere contains a layer of ozone gas which protects us from the harmful ultraviolet rays of the Sun.
- In the higher levels of the stratosphere, the temperature increases with height due to the absorption of UV rays by the ozone layer.
- The upper part of stratosphere is known as stratopause.
- This is the third layer of the atmosphere and lies above the stratosphere up to a height of 80 km.
- It is in this layer that the meteorites burn when they enter into the atmosphere from space.
- The upper layer of mesosphere is known as the mesopause.
Thermosphere or Ionosphere
- This layer extends from 80-400 km.
- Temperature increases drastically in this layer and can go up to 1,480°C. It is because the molecules in this layer absorb the Sun’s UV rays.
- The thermosphere helps in the transmission of radio waves as the latter is reflected back to the Earth by this layer.
- It is the uppermost layer of the Earth and has a very thin layer of air.
- Light gases like helium and hydrogen float into the space from this layer due to lack of gravity.
- This layer extends from 480 km to 960 km above the Earth.
- Temperature increases with height in this layer. The temperature may well go beyond 1,600°C.
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