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

$A$ plane polarized monochromatic $EM$ wave is travelling in a vacuum along the $z$-direction such that at $t = t_1$,it is found that the electric field is zero at a spatial point $z_1$. The next zero that occurs in its neighborhood is at $z_2$. The frequency of the electromagnetic wave is:

$A$ point source of electromagnetic radiation has an average power output of $800 \ W$. Find the maximum value of the magnetic field at a distance of $3.5 \ m$ from the source.

In a plane electromagnetic wave,the maximum value of the electric field component is $4.4 \ Vm^{-1}$. The intensity of the wave is nearly (in $mW \ m^{-2}$)

The electric field intensity of an electromagnetic wave is ....... to the distance it has traveled.

An electromagnetic wave propagating through a vacuum is described by $E = E_0 \sin(kx - \omega t)$ and $B = B_0 \sin(kx - \omega t)$. Which of the following equations is true?