Question

Assertion : UV radiation causes photodissociation of ozone into O₂ and O, thus causing damage to the stratospheric ozone layer.

Reason : Ozone hole is resulting in global warming and climate change.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

Correct option (b) 

Explanation :

Stratosphere zone of earth's atmosphere contains a layer of ozone (O₃) which prevents the earth surface from about 99% of incoming solar ultra violet radiations. The primary chemicals responsible for ozone depletion are a group of chlorine containing compounds called chlorofluorocarbons (CFCs) used as coolants in refrigerators and air conditioners and propellants for aerosol cans and foam blowing agents for insulation and packaging and also as solvents. After their release into troposphere CFCs go to stratosphere when these are broken down by ultraviolet radiations releasing chlorine or bromine which break O₃ molecules into O₂ and O. Due to depletion of O₃ layer higher levels of ultra violet rays reach earth surface. Depletion in the concentration of ozone over a restricted area is called ozone hole. Ozone depletion results in problems like skin cancer, cataract animals becoming blind, mutations, inhibiting photosynthesis, decreases in productivity. Decreased photosynthetic activity will increase O₂ concentration of the atmosphere resulting in global warming.