In an electromagnetic wave,the amplitude of the electric field is $1 \ V/m$ and the frequency of the wave is $5 \times 10^{14} \ Hz$. The wave propagates in the positive $Z$-direction. The average energy density of the electric field in this wave is ........ $J \ m^{-3}$.

The refractive index of the ionosphere is ........

Consider an electromagnetic wave propagating in a vacuum. Choose the correct statement.

$A$ mathematical representation of an electromagnetic wave is given by the two equations $E = E_{max} \cos(kx - \omega t)$ and $B = B_{max} \cos(kx - \omega t)$,where $E_{max}$ is the amplitude of the electric field and $B_{max}$ is the amplitude of the magnetic field. What is the intensity $I$ in terms of $E_{max}$ and universal constants $\mu_0, \epsilon_0$?

The energy associated with the electric field is $(U_E)$ and with the magnetic field is $(U_B)$ for an electromagnetic wave in free space. Then

In the propagation of electromagnetic waves,the angle between the direction of propagation and the plane of polarisation is......$^o$.