A plane electromagnetic wave in the visible region is moving along z-direction. The frequency of the wave is `6xx10^14Hz`, and the electric field at any point is varying sinusoidally with time with an amplitude of `2Vm^-1`. Calculate
(i) average energy density of the electric field and
(ii) average energy density of the magnetic field.

Explanation

Here, `v=6xx10^14Hz, E_0=2Vm^-1`
(i) Average energy density of the electric field
`u_E=1/4in_0E_0^2=1/4xx(8.85xx10^-12)xx2^2`
`=8.85xx10^-12Jm^-3`
(ii) Average energy density of magnetic field
`u_B=(B_0^2)/(4mu_0)=1/4xx((E_0//c)^2)/(mu_0)=1/4 (E_0^2)/(mu_0c^2)`
`=1/4xx(2^2)/((4pixx10^-7)xx(3xx10^8)^2)`
`=8.85xx10^-12Jm^-3`