Question

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). 
Assertion (A): Electromagnetic waves carry energy but not momentum. 
Reason (R): Mass of a photon is zero. 
In the light of the above statements, choose the most appropriate answer from the options given below:

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

Hint:

Remember that the momentum of a photon is not directly related to its mass (since it has zero rest mass), but instead is given by the energy of the photon divided by the speed of light.

Answer 1

The Correct Option is C

- Assertion (A) is true: Electromagnetic waves are confirmed to carry both energy and momentum. Their momentum is directly proportional to their energy, expressed as \( p = \frac{E}{c} \), where \( E \) represents the wave's energy and \( c \) denotes the speed of light.
- Reason (R) is also true: While photons, the constituents of electromagnetic waves, possess zero rest mass, this characteristic does not negate their ability to carry momentum. Photons convey momentum irrespective of their lack of rest mass. However, Reason (R) does not provide a valid explanation for Assertion (A), as the absence of rest mass in photons does not preclude them from possessing momentum. Therefore, the correct conclusion is (3).