$A$ laser beam is operating at $100 \,mW$. The amount of energy stored by $90 \,cm$ length of this laser beam will be

Assertion : Environmental damage has increased the amount of ozone in the atmosphere.
Reason : Increase of ozone increases the amount of ultraviolet radiation on earth.

For an $EM$ wave,the electric and magnetic fields are $300 \ V m^{-1}$ and $7.9 \ A m^{-1}$ respectively. The maximum rate of energy flow is, (in $W m^{-2}$)

The electric field of a plane electromagnetic wave is given by $\overrightarrow{E} = E_{0} \frac{\hat{i}+\hat{j}}{\sqrt{2}} \cos (kz+\omega t)$. At $t=0$,a positively charged particle is at the point $(x, y, z) = (0, 0, \frac{\pi}{k})$. If its instantaneous velocity at $t=0$ is $v_{0} \hat{k}$,the force acting on it due to the wave is

Generation,propagation,and detection of electromagnetic waves is the basis of:

This question has Statement $-1$ and Statement $-2.$ Of the four choices given after the Statements,choose the one that best describes the two Statements.
Statement $-1:$ Short wave transmission is achieved due to the total internal reflection of the $e-m$ wave from an appropriate height in the ionosphere.
Statement $-2:$ Refractive index of the ionosphere is independent of the frequency of $e-m$ waves.