Question

An electromagnetic wave contains non-zero energy density associated with it. It has both electric and magnetic fields associated with it. Then

• A. In free space with RMS value of electric field as $E$, the average energy density associated with electric field is $\frac{{ϵ}_0{E}^2}{2}$.
  
• B. In free space with RMS value of magnetic field as $B$, the average energy density associated with magnetic field is $\frac{B^2}{2{\mu }_0}$.
• C. Contribution of electric field to average energy density is double to that by magnetic field.
• D. Both options $\left(\text{A}\right)$ and $\left(\text{B}\right)$ are correct.

Answer 1

The correct option is D Both options $\left(\text{A}\right)$ and $\left(\text{B}\right)$ are correct.

Contribution of electric field and magnetic field to average energy density is equal. The average energy density associated with fields is
$u_E=\frac{{ϵ}_0{E}^2}{2}\text{and}{u}_B=\frac{B^2}{2{\mu }_0}$