Question

A sinusoidal electromagnetic wave from a radio station passes perpendicularly through an open window that has area 0.320 m2. at the window, the electric field of the wave has rms value 0.0195 v/m. how much energy does this wave carry through the window during a 26.0-s commercial?

Answer 1

Remember, half of the energy in an EM wave is in the E field, the rest is in the B field. Thus, multiply E field energy by 2.
To calculate the energy of the wave you must then use the following equation: W = A*t*c*2*(1/2*E^2*Eo). Where, A = Area, t = time, c = speed of light (which is a constant), E = Electric field, E0 = vacuum permittivity (8.85*10^-12 Nm^2/C^2). Substituting W =(0.320)*(26)*(3*10^8)*(2)*((1/2)*(1.95*10^-2)^2*(8.854*10^-12)) = 8.40*10^-6 J