Question

Explain the structure of atmosphere with suitable diagram.

Answer 1

1. Troposphere:

This is the lowest layer of atmosphere and it is very important for all the living organisms because all the activities and aspects related with weather e.g. Evaporations, condensation, precipitation, storm, lightening etc. originate in this sphere. Around 75% mass of gases and nearly all water vapours and aerosols are present in this layer.

2. Stratosphere:

This sphere starts from 12 to16 kilometers above the Earth surface and extend upto 50 kilometers known for isothermal characteristics also. Although scientists have different views about the height, width and temperature but they all agree on one point that at the lower layer of this sphere temperature does not change with increase in height but at the height of 20 KM in upper stratosphere temperature starts increasing because of absorption of ultra-violet rays by ozone gases. At the height of 50 KM it becomes 0° Celsius (32°F).

Region where ozone gas is present in abundance is also known as ozone layer. This gas is present in abundance between 15 to 35 kilometers above the Earth surface, which originates when oxygen molecule disintegrates into two atoms of oxygen and then integrating back into a molecule. Molecules of ozone layer are not stable, their origin and disintegration is a gradual and continuous process.

3. Mesosphere:

Above the upper boundary of stratosphere, which extends from 50 kms. above surface of Earth, is mesosphere, upto 80 kms. In this layer temperature again starts decreasing with the increase in height and at the upper boundary of this layer it touches down to -80°C point. Air pressure is very low in this layer. At the height of 50 kms it is 1 mb and at height of 80 kms it drops to 0.01 mb.

4. Ionosphere:

The height of this sphere extends from 80 to 640 kms above surface of Earth. Credit of discovering this layer goes to scientists Kennelly and Heaviside who, with the help of radio waves proved that the atoms and molecules of the gases present in this layer get electrically changed by the addition and removal of electrons due to the effect of ultraviolet, Xray and Gama rays.

Short wavelength rays of solar energy (UV, X, L) get absorbed by molecules and atoms of nitrogen and oxygen because of which temperature increases upto 1000°C in this scanty pressure layer of atmosphere. Because of scanty air pressure, temperature here is quite different as compared to the temperature felt at the surface of Earth.

5. Exosphere:

This is the outermost layer of atmosphere and we do not have much information about this layer. It lies above the height of 640 kms. Only Helium and hydrogen are found in this layer. Moreover the density of this layer is very low.

Answer 2

The structure of the atmosphere along with the diagram is given below:

• The atmosphere is divided majorly into five layers. These are:

1. Troposphere: It is the lowest layer from the surface of the Erath and extends up to 13km from the surface. It is the most important too. Oxygen exists in this layer.
2. Stratosphere: It is the second layer from the Earth and extends up to a height of 50km. It contains the ozone layer. The ozone layer protects us from the harmful ultraviolet radiation from the Sun.
3. Mesosphere: It lies above the stratosphere and extends up to a height of 80kms.
4. Thermosphere or Ionosphere: It extends from 80-400km. The molecules in this layer absorb the Sun’s radiations (particularly UV rays). This makes the layer very hot.
5. Exosphere: It is the Earth's uppermost layer and extends from 480 km to 960 km above the Earth. This layer lacks gravity and thus has a very thin layer of air.