Question

Assertion (A): Ozone at higher levels of atmosphere is a product of UV radiation acting on oxygen molecule.
Reason (R): The higher energy of UV splits apart some molecular \( O_2 \).

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Ozone formation in stratosphere: \[ O_2 \xrightarrow{UV} 2O \] \[ O + O_2 \rightarrow O_3 \] UV radiation is essential for both splitting oxygen and forming ozone!

Answer 1

The Correct Option is A

Step 1: Analyze Assertion (A).
Assertion (A): "Ozone at higher levels of atmosphere is a product of UV radiation acting on oxygen molecule."

• Ozone (\(O_3\)) is formed in the stratosphere through a series of reactions involving UV radiation and oxygen molecules (\(O_2\)).
• This is a well-established scientific fact about the ozone layer.
• Therefore, Assertion (A) is TRUE.

Step 2: Analyze Reason (R).
Reason (R): "The higher energy of UV splits apart some molecular \(O_2\)."

• UV radiation (particularly UV-C) has high energy that can break the bond between oxygen atoms in an \(O_2\) molecule.
• This process is called photodissociation: \(O_2 \xrightarrow{UV} O + O\)
• Therefore, Reason (R) is TRUE.

Step 3: Check if Reason (R) correctly explains Assertion (A).
The formation of ozone involves two steps: 1. UV radiation splits oxygen molecules into oxygen atoms (Reason R): \[ O_2 \xrightarrow{UV} O + O \] 2. These oxygen atoms combine with other oxygen molecules to form ozone: \[ O + O_2 \rightarrow O_3 \] Thus, the splitting of \(O_2\) by UV radiation (Reason R) is the first and essential step in the formation of ozone (Assertion A). Therefore, Reason (R) is the correct explanation of Assertion (A). Final Answer: (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).