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

detailed solution

Correct option is A

Energy contained per unit volume through which electromagnetic wave is propagating is sum of energy of electric field and energy of magnetic field. U=UE+UB=12∈o E2+12B2μ0Where E and B are Sinusoidal functionE=E0sinω(t−XC) &  B=Bosinω(t−XC)⇒UE=12∈0E2=12E 02sin2ω(t−XC)  ⇒UE=12×E021−cos2ω(t−XC)2Hence the frequency of UE is double than that of electromagnetic wave. Similarly the frequency of UB is double than that of electromagnetic wave.