The unit of $\sqrt{\frac{2 I}{\varepsilon_0 c}}$ is
($I$: intensity of an electromagnetic wave,$c$: speed of light)

The sun delivers $10^{3} \,W m^{-2}$ of electromagnetic flux on the Earth's surface. The total power that is incident on a roof of dimensions $6 \,m \times 30 \,m$ is . . . . . . .

An electromagnetic wave has its electric and magnetic fields given by $\vec{E}(t) = \vec{E}_m \sin(kx - \omega t)$ and $\vec{B}(t) = \vec{B}_m \sin(kx - \omega t)$. If the directions of $\vec{E}_m$ and $\vec{B}_m$ are in the direction of $\hat{i} + \hat{j}$ and $\hat{i} - \hat{j}$ respectively,the unit vector that gives the direction of propagation of the wave is:

$A$ source emits electromagnetic waves of frequency $8.2 \times 10^6 \text{ Hz}$. What is the wavelength of these waves in meters?

$A$ laser beam of pulse power $10^{12} \ W$ is focused on an object area of $10^{-4} \ cm^2$. The energy flux in $W/cm^2$ at the point of focus is:

Electromagnetic waves consist of periodically oscillating electric and magnetic vectors: