Question

Assertion : UV radiation causes photodissociation of ozone into $O _{2}$ and $O$, thus causing damage to the stratospheric ozone layer.
Reason : Ozone hole is resulting in global warming and climate change.

• A. If both Assertion and Reason are true and the reason is the correct explanation of the assertion
• B. If both Assertion and Reason are true but the reason is not the correct explanation of the assertion
• C. If Assertion is true statement but Reason is false
• D. If both Assertion and Reason are false statements

Answer 1

Answer: (A)

UV radiation does not cause photodissociation of ozone into $O _{2}$ and $O$ instead it takes part in the formation of ozone into two steps.
In the first step, UV radiation breaks apart the two atoms of oxygen and in the second step one of the liberated atom (O) joins another oxygen molecule $\left( O _{2}\right)$ to form ozone $\left( O _{3}\right)$.
$O _{2} \xrightarrow{\text { UV radiation }}O + O$
$O _{2}+ O \xrightarrow{\text { UV radiation }} \underset{\text { (ozone) }}{ O _{3}}$
Due to human activities, the ozone layer in the stratosphere becomes start thinning which is also called ozone hole. Ozone hole is resulting in rain failure, increase in radiation, cancers (skin) and reduction in crop production.
Global warming and climate changes are mainly due to green-house gases $\left( CO _{2}, NO _{ x }\right)$.