Question

The energy contained in a small volume through which an electromagnetic wave is passing oscillates with

(a) zero frequency 

(b) the frequency of the wave

(c) half the frequency of the wave

(d) double the frequency of the wave.

Answer 1

(d) double the frequency of the wave.

Comments

How, reason behind it?

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The energy per unit volume contained in electromagnetic waves is
U = 1/2ɛE^2 + B^2/2μ
If the electric field is represented by a form E_o cos( wt - kx) the energy can be modified into the form, U_o cos(2wt - k'x) + c
Hence the frequency of oscillation of the electric field is double.