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

The energy of an electromagnetic wave contained in a small volume oscillates with

An electric bulb is rated as $200 \,W$. What will be the peak magnetic field ($\times 10^{-8}\, T$) at $4\, m$ distance produced by the radiations coming from this bulb$?$ Consider this bulb as a point source with $3.5 \%$ efficiency.

$TV$ waves have a wavelength range of $1-10 \,meter$. Their frequency range in $MHz$ is

The electric field of a plane electromagnetic wave is given by

$\overrightarrow{\mathrm{E}}=\mathrm{E}_{0} \frac{\hat{\mathrm{i}}+\hat{\mathrm{j}}}{\sqrt{2}} \cos (\mathrm{kz}+\omega \mathrm{t})$ At $\mathrm{t}=0,$ a positively charged particle is at the point $(\mathrm{x}, \mathrm{y}, \mathrm{z})=\left(0,0, \frac{\pi}{\mathrm{k}}\right) .$ If its instantaneous velocity at $(t=0)$ is $v_{0} \hat{\mathrm{k}},$ the force acting on it due to the wave is

If ${\varepsilon _0}$ and ${\mu _0}$ are respectively, the electric permittivity and the magnetic permeability of free space. $\varepsilon $ and $\mu $ the corresponding quantities in a medium, the refractive index of the medium is