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

Question

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

G1 Physics · Accepted Answer

For an electromagnetic wave, E = E₀ sin(ωt − kx) Energy density is proportional to E²: u ∝ sin²(ωt − kx) Using sin²θ = [1 − cos2θ]/2, the oscillatory part contains angular frequency 2ω. Therefore the energy density oscillates with twice the wave frequency. Hence option A follows.