Electromagnetic Waves · Question 24

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the most appropriate answer from the options given below :

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 false but (R) is true
4. (A) is true but (R) is false

Answer

(3) (A) is false but (R) is true

Solution

Electromagnetic waves carry both energy and momentum. A wave carrying energy U carries momentum p = Uc; this momentum transfer produces radiation pressure on a surface.

Assertion (A) is false.

The rest mass of a photon is zero (its energy and momentum are related by E = pc).

Reason (R) is true.

Answer: (3)