The electric field associated with an $e.m.$ wave in vacuum is given by $\vec E = \hat i\,40\,\cos \,\left( {kz - 6 \times {{10}^8}\,t} \right)$. where $E$, $z$ and $t$ are in $volt/m$, meter and seconds respectively. The value of wave factor $k$ is ....... $m^{-1}$.

Energy stored in electromagnetic oscillations is in the form of

All electromagnetic wave is transporting energy in the negative $z$ direction. At a certain point and certain time the direction of electric field of the wave is along positive y direction. What will be the direction of the magnetic field of the wave at that point and instant?

An electromagnetic wave of intensity $50\,Wm^{-2}$ enters in a medium of refractive index $’ n’$ without any loss . The ratio of the magnitudes of electric fields, and the ratio of the magnitudes of magnetic fields of the wave before and after entering into the medium are respectively. Given by

What is force exerted on surface having area of $10\, cm^2$ due to radiation of Sun ? 

For the plane electromagnetic wave given by $\mathrm{E}=\mathrm{E}_0 \sin (\omega \mathrm{t}-\mathrm{kx})$ and $\mathrm{B}=\mathrm{B}_0 \sin (\omega \mathrm{t}-\mathrm{kx})$, the ratio of average electric energy density to average magnetic energy density is