In a plane electromagnetic wave,$U_E$ and $U_B$ are the average energy densities of the electric field and magnetic field,respectively. Then,which of the following is the correct option?

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

An electromagnetic wave of frequency $3 \, GHz$ enters a dielectric medium of relative electric permittivity $2.25$ from vacuum. The wavelength of this wave in that medium will be $....... \times 10^{-2} \, cm$.

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 electric field of an electromagnetic wave travelling through a medium is given by $\overline{E}(x,t) = 25 \sin(2.0 \times 10^{15}t - 10^{7}x)\hat{n}$. The refractive index of the medium is . . . . . . . (All given measurements are in $SI$ units)

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 $\times 10^{7}\, m/s$.