Question

In a plane e.m. wave of frequency `1.5xx10^12Hz`, the amplitude fo the magnetic field is `6.0xx10^-6T`.
(a) Calculate the amplitude of the electric field.
(b) What is the total average energy density of the e.m. wave?

Answer 1

Correct Answer - (a) `1.8xx10^3 Vm^-1 (b) 1.4xx10^-5J//m^-3`
Here, `v=1.5xx10^(12)Hz, B_0=6.0xx10^-6T`
(a) Amplitude of electric field,
`E_0=CB_0=(3xx10^8)xx(6.0xx10^-6)`
`=1.8xx10^3Vm^-1`
(b) Total average energy density is
`U_(av)=1/2in_0E_0^2=1/2(8.85xx10^(-12))xx(1.8xx10^3)^2`
`=1.4xx10^-5Jm^-3`