Assume a bulb of efficiency $2.5\%$ as a point source. The peak value of the electric field produced by the radiation coming from a $100\, W$ bulb at a distance of $3\, m$ is approximately.....$V\,m^{-1}$.

$A$ $27\, mW$ laser beam has a cross-sectional area of $10\, mm^2$. The magnitude of the maximum electric field in this electromagnetic wave is given by: $........\, kV/m$. [Given permittivity of free space $\epsilon_0 = 9 \times 10^{-12}\, SI\, units$, speed of light $c = 3 \times 10^8\, m/s$]

Intensity of sunlight is observed as $0.092 \, W/m^2$ at a point in free space. What will be the peak value of the magnetic field at that point? (Given: $\epsilon_0 = 8.85 \times 10^{-12} \, C^2 N^{-1} m^{-2}$,$c = 3 \times 10^8 \, m/s$)

$A$ plane electromagnetic wave of wavelength $\lambda$ has an intensity $I$. It is propagating along the positive $Y$-direction. The allowed expressions for the electric and magnetic fields are given by:

The electron density of $E, F_1,$ and $F_2$ layers of the ionosphere is $4 \times 10^{11} \, m^{-3}, 9 \times 10^{11} \, m^{-3},$ and $16 \times 10^{11} \, m^{-3}$ respectively. What is the ratio of the critical frequencies for the reflection of radio waves?

An electromagnetic wave with angular frequency $\omega$ and wavelength $\lambda$ propagates in the $+y$ direction. Its magnetic field is directed along the $-x$ direction. The vector expression for the associated electric field (with amplitude $E_0$) is ...........