The electric field for a plane electromagnetic wave travelling in the $+y$ direction is shown. Consider a point where $\vec E$ is in the $+z$ direction. The $\vec B$ field is

$A$ sky wave with a frequency of $55 \text{ MHz}$ is incident on the $D$-region of the ionosphere at an angle of $45^\circ$. What is the angle of refraction? (The electron density in the $D$-region is $400 \text{ electrons/cm}^3$).

Assertion : Radio waves can be polarised.
Reason : Sound waves in air are longitudinal in nature.

If $\overrightarrow E$ and $\overrightarrow B$ are the electric and magnetic field vectors of electromagnetic waves,then the direction of propagation of the electromagnetic wave is along the direction of:

$A$ radio can tune in to any station in the $7.5\; MHz$ to $12\; MHz$ band. What is the corresponding wavelength band?

$A$ $27\, mW$ 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 $c = 3 \times 10^8\, m/s$]