JEE Main 2019 — Electromagnetic Waves Question with Solution

The average energy density of electric field is given by

$u_E=\frac{1}{2}\epsilon {E_0}^2$

Here, $E_0$ is the maximum value of electric field.

The average energy density of magnetic field is given by

$u_B=\frac{{B_0}^2}{2\mu }$

Here, $B_0$ is the maximum value of magnetic field.

The speed of light is given by $c^2=\frac{1}{\mu \epsilon }$

Also, $E_0=c{B}_0$

So, $u_E=\frac{1}{2c^2\mu }{\left(c{B}_0\right)}^2=\frac{{B_0}^2}{2\mu }=u_B$

As the energy density of electric field and magnetic field are equal, the energy associated for equal volume will also be equal.