Q 12-08-192JEE MainJEE Main 2019 (9 Jan, Shift 2)Easy
The energy associated with electric field is $(U_E)$ and with magnetic field is $(U_B)$ for an electromagnetic wave in free space. Then:
Answer: (B) $U_E = U_B$
In free space $E = cB$ and $c^2 = \dfrac{1}{\mu_0\epsilon_0}$, so
$$u_E = \tfrac12\epsilon_0E^2 = \tfrac12\epsilon_0c^2B^2 = \frac{B^2}{2\mu_0} = u_B$$
The electric and magnetic energies are equal: $U_E = U_B$.
Solution by Sreeraj P, M.Sc Physics