The electromagnetic wave of the radiation field from a wire antenna travels towa

Question

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of the paper (which is in the –z direction). At time t = 0 s, the wave strikes the paper at normal incidence. The magnetic field vector at point O in the figure points in the –y direction and has a magnitude of 4.0 *10^8 T. The frequency of the wave is 1.0*10^16 Hz. What is the intensity of of the electromagnetic wave at time t=0s? The answer key says its 0.38 W/m^2. I tried solving for energy density and then plugging it back into the instensity equation of S = cu. What am I missing?

Explanation / Answer

u = B^2 / mu ( total energy density both electric and magnetic)

u = (4 * 10^-8)^2 / ( 4 * pi * 10^-7) = 1.273 * 10^-9

S = cu = 1.273 * 10^-9 * 3 * 10^8 = 0.38W/m^2

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