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 :

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

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

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

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

answer is B.

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Detailed Solution

This statement is incorrect. Electromagnetic (EM) waves do carry both energy and momentum.

The energy of an EM wave is given by:

where $h$ is Planck's constant and $f$ is the frequency.

The momentum of a photon (which makes up EM waves) is given by:

This shows that EM waves do carry momentum, which is why radiation pressure exists.

Thus, Assertion (A) is incorrect.

This statement is correct. Photons have zero rest mass but still carry momentum due to their wave nature.

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