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JEE Main 2026 Apr 5 Shift 2, Physics Q14: Electromagnetic Waves

JEE Main2026Apr 5, Shift 2Physics
Q.

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): The electromagnetic wave exerts pressure on the surface on which they are allowed to fall.

Reason (R): There is no mass associated with the electromagnetic waves.

In the light of the above statements, choose the correct answer from the options given below:

  1. A

    Both (A) and (R) are true and (R) is the correct explanation of (A)

  2. B

    Both (A) and (R) are true but (R) is not the correct explanation of (A)

  3. C

    (A) is true but (R) is false

  4. D

    (A) is false but (R) is true

Solution

EM waves do exert radiation pressure because they carry momentum ; this is the standard result. Photons have zero rest mass yet still carry momentum, so the Reason statement that there is no mass associated with EM waves is also correct.

However, the absence of rest mass is not the reason for the existence of radiation pressure. The pressure exists because of momentum transfer, not because of any mass-related argument.

Both (A) and (R) are true, but (R) is not the correct explanation of (A).

Concept behind this question

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