$A$ plane electromagnetic wave of frequency $100 \, MHz$ is travelling in vacuum along the $x$-direction. At a particular point in space and time,$\overrightarrow{B} = 2.0 \times 10^{-8} \hat{k} \, T$ (where $\hat{k}$ is the unit vector along the $z$-direction). What is $\overrightarrow{E}$ at this point?

The transverse nature of electromagnetic waves is demonstrated by which of the following phenomena?

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

The oscillating electric and magnetic vectors of an electromagnetic wave are oriented along

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

Suppose that the electric field part of an electromagnetic wave in vacuum is $E = \{(3.1 \; N/C) \cos [(1.8 \; rad/m) y + (5.4 \times 10^{6} \; rad/s) t] \} \hat{i}$.
$(a)$ What is the direction of propagation?
$(b)$ What is the wavelength $\lambda$?
$(c)$ What is the frequency $\nu$?
$(d)$ What is the amplitude of the magnetic field part of the wave?
$(e)$ Write an expression for the magnetic field part of the wave.