Q. Consider the following statements:
1. The temperature in mesosphere increases with increase in altitude.
2. Ozone layer is present in stratosphere.
3. Radio waves transmitted from the earth are reflected back to the earth by ionosphere.
Which of the statements above given is/are correct?

[A] 1 and 2 only

[B] 2 and 3 only

[C] 1 and 3 only

[D] 1, 2 and 3

Answer: B
Notes:

The atmosphere consists of different layers with varying density and temperature. Density is highest near the surface of the earth and decreases with increasing altitude.  

  • The column of atmosphere is divided into five different layers depending upon the temperature condition. They are: troposphere, stratosphere, mesosphere, thermosphere and exosphere. 
  • The troposphere 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 stratosphere 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 intense, harmful form of energy. 
  • The mesosphere lies above the stratosphere, which extends up to a height of 80 km.  
  • In this layer, once again, temperature starts decreasing with the increase in altitude and reaches up to minus 100°C at the height of 80 km.  
  • The upper limit of mesosphere is known as the mesopause.  
  • The ionosphere is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence, it is known as ionosphere.  
  • Radio waves transmitted from the earth are reflected back to the earth by this layer. Temperature here starts increasing with height.  
  • The uppermost layer of the atmosphere above the thermosphere is known as the exosphere. This is the highest layer but very little is known about it.  

Source: ICSE – Total Geography