When an electromagnetic wave passes through a dielectric medium,the transmitted wave has:

An electron is constrained to move along the $y$-axis with a speed of $0.1 c$ ($c$ is the speed of light) in the presence of an electromagnetic wave,whose electric field is $\overrightarrow{E} = 30 \hat{j} \sin(1.5 \times 10^7 t - 5 \times 10^{-2} x) \, V/m$. The maximum magnetic force experienced by the electron will be: (given $c = 3 \times 10^8 \, m/s$ and electron charge $q = 1.6 \times 10^{-19} \, C$)

$A$ plane electromagnetic wave of intensity $6 \, W/m^2$ strikes a small mirror of area $30 \, cm^2$,held perpendicular to the approaching wave. The momentum transmitted in $kg \cdot m/s$ by the wave to the mirror each second will be:

Answer the following questions:
$(a)$ Long distance radio broadcasts use short-wave bands. Why?
$(b)$ It is necessary to use satellites for long distance $TV$ transmission. Why?
$(c)$ Optical and radio telescopes are built on the ground but $X$-ray astronomy is possible only from satellites orbiting the earth. Why?
$(d)$ The small ozone layer on top of the stratosphere is crucial for human survival. Why?
$(e)$ If the earth did not have an atmosphere,would its average surface temperature be higher or lower than what it is now?
$(f)$ Some scientists have predicted that a global nuclear war on the earth would be followed by a severe 'nuclear winter' with a devastating effect on life on earth. What might be the basis of this prediction?

In an electromagnetic wave,the amplitude of the electric field is $1 \ V/m$ and the frequency of the wave is $5 \times 10^{14} \ Hz$. The wave propagates in the positive $Z$-direction. The average energy density of the electric field in this wave is ........ $J \ m^{-3}$.

The electric field of a plane electromagnetic wave is given by $\vec E = E_0 \hat i \cos(kz) \cos(\omega t)$. The corresponding magnetic field $\vec B$ is then given by: