The electromagnetic flux from the sun reaching the earth is $10^3 \, W/m^2$. The power incident on a roof of dimensions $8 \, m \times 20 \, m$ is ..... $W$.

Write the equation for the energy density of electromagnetic waves.

How much time will it take for information to propagate over a distance of $30 \, km$ in space?

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

Suppose that the electric field part of an electromagnetic wave in vacuum is $E = \{(3.1 \; N/C) \cos [(1.8 \; rad/m) y + (5.4 \times 10^{6} \; rad/s) t] \} \hat{i}$.
$(a)$ What is the direction of propagation?
$(b)$ What is the wavelength $\lambda$?
$(c)$ What is the frequency $\nu$?
$(d)$ What is the amplitude of the magnetic field part of the wave?
$(e)$ Write an expression for the magnetic field part of the wave.

Calculate the electric and magnetic fields produced by the radiation coming from a $100\; W$ bulb at a distance of $3\; m$. Assume that the efficiency of the bulb is $2.5\%$ and it is a point source.