An optical fibre communication system works on a wavelength of $1.3 \mu m$. The number of subscribers it can feed if a channel requires $20 \ kHz$ is:

$A$ message signal of frequency $100\, MHz$ and peak voltage $100\, V$ is used to execute amplitude modulation on a carrier wave of frequency $300\, GHz$ and peak voltage $400\, V$. The modulation index and difference between the two sideband frequencies are:

$A$ transmitter supplies $9 \,kW$ to the aerial when unmodulated. The power radiated when modulated to $40\%$ is........$kW$

In an amplitude modulation with modulation index $0.5$,the ratio of the amplitude of the carrier wave to that of the side band in the modulated wave is

$A$ signal emitted by an antenna from a certain point can be received at another point on the Earth's surface in the form of:

The amplitude of the side bands of the modulated signal, if the carrier signal and message signal amplitudes are $25 \,V$ and $5 \,V$ respectively, is (in $\,V$)