To radiate a wave of frequency $1 \text{ kHz}$ efficiently,what should be the minimum length of the antenna in $km$?

What is the modulation index of an over-modulated wave?

If the length of an antenna is $150 \,cm$,the transmission frequency is . . . . . . $MHz$. (Speed of light in vacuum $= 3 \times 10^8 \,ms^{-1}$)

In amplitude modulation,the amplitude of the $.......$ wave varies in proportion to the instantaneous value of the $.......$ wave.

If a $TV$ transmission antenna covers a radius of $128 \, km$,what should be the height of the antenna in $m$?

$A$ radar has a power of $1 \text{ kW}$ and operates at a frequency of $10 \text{ GHz}$. If it is located on top of a mountain at a height of $500 \text{ m}$,what is the maximum distance in $\text{km}$ up to which it can detect objects on the Earth's surface? (Radius of the Earth $R = 6.4 \times 10^{6} \text{ m}$)