If $c$ is the speed of electromagnetic waves in vacuum,its speed in a medium of dielectric constant $K$ and relative permeability $\mu_r$ is:

The electric field of a plane electromagnetic wave propagating along the $x$-direction in vacuum is $\overrightarrow{E} = E_{0} \hat{j} \cos(\omega t - kx)$. The magnetic field $\overrightarrow{B}$ at the moment $t = 0$ is:

$A$ plane electromagnetic wave with electric field amplitude $E_0$ and magnetic field amplitude $B_0$ is incident on a surface. If the total energy transferred to the surface in time $t$ is $U$,then the magnitude of the total momentum delivered to the surface for complete absorption is

Electromagnetic waves are:

If the amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum is $270 \ nT$,the amplitude of the electric field part of the wave is: (in $NC^{-1}$)

$A$ light wave is travelling along the $y$-direction. If the corresponding $\vec E$ vector at any time is along the $x$-axis,the direction of the $\vec B$ vector at that time is along: