Question

At some instant and location, the electric field associated with an electromagnetic wave in vacuum has the strength 97.3 V/m. Find the magnetic field strength B, the total energy density u, and the power flow per unit area, all at the same instant and location. B= т U = J/m3 power flow per unit area: W/m2

Answer 1

Magnetic field corresponding to an electric field E, using c as the velocity of light is given by

$B=\frac{E}{c}=\frac{97.3}{3\times10^8}\ T=3.24\times10^{-7}\ T$

Total energy density is

Energy density is given by

u = EP

epsilon0 denotes the permittivity due to free space

$u=\epsilon_0E^2=8.85\times10^{-12}\times97.3^2\ J/m^3=8.38\times10^{-8}\ J/m^3$

Power flow per unit area is

$P=\epsilon_0 cE^2=8.85\times10^{-12}\times3\times10^8\times97.3^2\ W/m^2=25.14\ W/m^2$