The energy of an electromagnetic wave contained in a small volume oscillates with (a) double the frequency of the wave (b) the frequency of the wave (c) half the frequency of the wave (d) zero frequency

Answer: (a). Energy density u ∝ E² = E₀² sin ²(ω t - kx) = (E₀²)/(2)[1 - cos 2(ω t - kx)] The varying part has angular frequency 2ω. So the answer is (a) double the frequency of the wave.

The energy of an electromagnetic wave contained in a small volume… | JEE Main 2023 (10 Apr, Shift 1)

Q13JEE Main 2023 · 10 APR · SHIFT 1Medium

Energy Density & Intensity

The energy of an electromagnetic wave contained in a small volume oscillates with

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Answer: (a)

Energy density $u \propto E^2 = E_0^2 \sin^2(\omega t - kx) = \tfrac{E_0^2}{2}[1 - \cos 2(\omega t - kx)]$
The varying part has angular frequency $2\omega$ .
So the answer is (a) double the frequency of the wave.

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