The unit of $\sqrt{\frac{2 I}{\varepsilon_0 c}}$ is
($I$: intensity of an electromagnetic wave,$c$: speed of light)

An electromagnetic wave of frequency $5\, GHz$ is travelling in a medium whose relative electric permittivity and relative magnetic permeability both are $2$. Its velocity in this medium is $\times 10^{7}\, m/s$.

Assertion $(A)$: Electromagnetic waves exert pressure,called radiation pressure.
Reason $(R)$: This is because they carry energy.

If the frequency of an electromagnetic wave is $60 \text{ MHz}$ and it travels in air along the $z$-direction,then the corresponding electric and magnetic field vectors will be mutually perpendicular to each other. The wavelength of the wave (in $\text{m}$) is:

The electron density of $E, F_1,$ and $F_2$ layers of the ionosphere is $4 \times 10^{11} \, m^{-3}, 9 \times 10^{11} \, m^{-3},$ and $16 \times 10^{11} \, m^{-3}$ respectively. What is the ratio of the critical frequencies for the reflection of radio waves?

The amplitude of the electric field in a parallel beam of plane electromagnetic waves of intensity $53.1 \ W \ m^{-2}$ is (Permittivity of free space $\epsilon_0 = 8.85 \times 10^{-12} \ C^2 \ N^{-1} \ m^{-2}$) (in $N \ C^{-1}$)