If the rms value of the electric field of electromagnetic waves at a distance of 3 m from a point source is $3 \mathrm{NC}^{-1}$, then the power of the source is

The magnitude of the electric field of a plane electromagnetic wave travelling in free space is $E$. If $\mu_0$ and $\varepsilon_0$ are respectively permeability and permittivity of the free space, then the magnitude of magnetic field of the wave is

A plane electromagnetic wave of frequency 25 MHz propagates in vacuum along positive $x$-direction. At a particular point in space and time, if the electric field is $63 \hat{\mathrm{j}} \mathrm{Vm}^{-1}$, then the magnitude of the magnetic field of the wave at this point at the same time is

If the magnetic field inside a solenoid is $B$, then the magnetic energy stored in it per unit volume is ( $c=$ speed of light in vacuum and $\varepsilon_0$ is permittivity of free space)