Question

In a plane e.m. wave, the electric field oscillates withe amplitude `20Vm^-1`. Find (a) energy density of electric field (b) energy density of magnetic field.

Answer 1

Correct Answer - `(a) 8.55xx10^(-10)J//m^3 (b) 8.55xx10^(-10)J//m^3`
(a) Average energy density of electric field,
`u_E=1/2in_0E_(rms)^2=1/2in_0((E_0)/(sqrt2))^2=1/4in_0 E_0^2`
(b) Average energy density of magnetic field
`=(B_(rms)^2)/(2mu_0)=((B_0//sqrt2)^2)/(2mu_0)=1/4 (B_0^2)/(mu_0)=1/4 in_0E_0^2`