The speed of an electromagnetic wave in a vacuum depends upon the source of radiation.

In a plane electromagnetic wave,the electric field oscillates with a frequency $2 \times 10^{10} \,s^{-1}$ and amplitude $40 \,Vm^{-1}$. The energy density due to the electric field is (given $\varepsilon_0 = 8.85 \times 10^{-12} \,Fm^{-1}$):

The electric field in a plane electromagnetic wave is given by $E_z = 60 \cos(5x + 1.5 \times 10^9 t) \text{ V/m}$. Then the expression for the corresponding magnetic field is (here subscripts denote the direction of the field):

The $rms$ value of the electric field of the light coming from the Sun is $720 \; N/C$. The average total energy density of the electromagnetic wave is

Electromagnetic waves are incident normally on a perfectly reflecting surface having surface area $A$. If $I$ is the intensity of the incident electromagnetic radiation and $c$ is the speed of light in vacuum,the force exerted by the electromagnetic wave on the reflecting surface is

The wavelength of an electromagnetic wave radiated by a charge oscillating with a frequency of $1 \, \text{kHz}$ is ..... $km$.