Given below are two statements : one is labelled as Assertion (A) and 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 :
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)(A) is true but (R) is false.
- (B)(A) is false but (R) is true.✓ Correct
- (C)Both (A) and (R) are true but (R) is not the correct explanation of (A).
- (D)Both (A) and (R) are true and (R) is the correct explanation of (A).
Answer: (B)
Solution
Electromagnetic waves carry both energy and momentum; the momentum of a photon is
so the claim that they carry energy but not momentum is false — the assertion is false.
A photon indeed has zero rest mass, which is true, but it still carries momentum because it always moves at speed ; a massless particle in relativity can carry nonzero momentum .
The assertion is false while the reason is true.
so the claim that they carry energy but not momentum is false — the assertion is false.
A photon indeed has zero rest mass, which is true, but it still carries momentum because it always moves at speed ; a massless particle in relativity can carry nonzero momentum .
The assertion is false while the reason is true.
JEE Main · 2025 · 29 Jan 2025 · Shift 1 · Single correct option