The energy density associated with the electric field $\overrightarrow{E}$ and magnetic field $\overrightarrow{B}$ of an electromagnetic wave in free space is given by ($\epsilon_0$ - permittivity of free space,$\mu_0$ - permeability of free space):

• A
  $U_E = \frac{E^2}{2\epsilon_0}, U_B = \frac{B^2}{2\mu_0}$
• B
  $U_E = \frac{E^2}{2\epsilon_0}, U_B = \frac{\mu_0 B^2}{2}$
• C
  $U_E = \frac{\epsilon_0 E^2}{2}, U_B = \frac{\mu_0 B^2}{2}$
• D
  $U_E = \frac{\epsilon_0 E^2}{2}, U_B = \frac{B^2}{2\mu_0}$