The magnetic field in a travelling electromagnetic wave has a peak value of $20 \ nT$. The peak value of electric field strength is ...... $Vm^{-1}$.

$A$ plane $EM$ wave travelling along $z-$ direction is described by $\vec E = E_0 \sin(kz - \omega t)\hat i$ and $\vec B = B_0 \sin(kz - \omega t)\hat j$. Show that:
$(i)$ The average energy density of the wave is given by $U_{av} = \frac{1}{4} \epsilon_0 E_0^2 + \frac{1}{4} \frac{B_0^2}{\mu_0}$.
$(ii)$ The time-averaged intensity of the wave is given by $I_{av} = \frac{1}{2} c \epsilon_0 E_0^2$.

$A$ charged particle oscillates about its mean equilibrium position with a frequency of $10^{9} \,Hz$. The frequency of electromagnetic waves produced by the oscillator is . . . . . . .

The $rms$ value of the electric field of the light coming from the sun is $720 \ N \ C^{-1}$. The average energy density of the electromagnetic wave is $...... \ J \ m^{-3}$.

The quantities $x = \frac{1}{\sqrt{\mu_{0} \varepsilon_{0}}}$,$y = \frac{E}{B}$,and $z = \frac{l}{CR}$ are defined,where $C$ is capacitance,$R$ is resistance,$l$ is length,$E$ is electric field,$B$ is magnetic field,and $\varepsilon_{0}, \mu_{0}$ are free space permittivity and permeability respectively. Then:

The velocity of an electromagnetic wave is in the direction of