Ncert Exercises & Solutions

Given below are two statements:

Assertion (A):	Ozone is destroyed by solar radiation in the upper stratosphere.
Reason (R):	Thinning of the ozone layer allows excessive UV radiations to reach the surface of the earth.

1.	Both (A) and (R) are true and (R) is the correct explanation of (A).
2.	Both (A) and (R) are true but (R) is not the correct explanation of (A).
3.	(A) is true but (R) is false.
4.	(A) is false but (R) is true.

Hint: Ozone is destroyed by CFCs in the upper stratosphere

The ozone layer is found in the stratosphere. The depletion of the ozone layer (Creation of ozone hole) is taking place due to

reaction with NO (produced from natural sources or human activity or in the exhaust gases of engines of supersonic planes)

or by reaction with chlorofluorocarbons (CFC's) called freons (produced from aerosol sprays used in propellents or from

refrigerators where they are used as coolants).

The ozone hole allows the UV radiations to pass through and reach us, increasing the chances of skin cancer.

Hence, Assertion is false but the reason is true.