A point source of $e. m.$ radiation has an average power output of $800\,W$ . The maximum value of electric field at a distance $4.0\,m$ from the source is...$V/m$

The electric fields of two plane electromagnetic plane waves in vacuum are given by

$\overrightarrow{\mathrm{E}}_{1}=\mathrm{E}_{0} \hat{\mathrm{j}} \cos (\omega \mathrm{t}-\mathrm{kx})$ and

$\overrightarrow{\mathrm{E}}_{2}=\mathrm{E}_{0} \hat{\mathrm{k}} \cos (\omega \mathrm{t}-\mathrm{ky})$

At $t=0,$ a particle of charge $q$ is at origin with a velocity $\overrightarrow{\mathrm{v}}=0.8 \mathrm{c} \hat{\mathrm{j}}$ ($c$ is the speed of light in vacuum). The instantaneous force experienced by the particle is 

A plane electromagnetic wave is travelling in the positive $X-$axis. At the instant shown electric field at the extremely narrow dashed rectangle is in the $-ve$  $z$ direction and its magnitude is increasing. Which diagram  correctly shows the direction and relative magnitudes of magnetic field at the edges of rectangle :-

The velocity of certain ions that pass undeflected through crossed electric field $E = 7.7\,k\,V /m$ and magnetic field $B = 0.14\,T$ is.....$km/s$

The velocity of electromagnetic radiation in a medium of permittivity ${\varepsilon _0}$  and permeability ${\mu _0}$ is given by 

A plane electromagnetic wave of frequency $25 \;MHz$ travels in free space along the $x$ -direction. At a particular point in space and time, $E = 6.3\,\hat j\;\,V/m$. What is $B$ at this point?