The height of a $TV$ transmission tower is $240 \ m$. Up to what distance can the transmission be received (in $km$)? (Radius of the Earth $R = 6.4 \times 10^6 \ m$)

The advantages of optical fiber communication over a two-wire transmission line or coaxial cable are . . . . . . .

$A$ transmitting antenna of height $20 \,m$ and a receiving antenna of height $h$ are separated by a distance of $40 \,km$ for satisfactory communication in line-of-sight $(LOS)$ mode. The value of $h$ is (Given: radius of Earth is $6400 \,km$). (in $\,m$)

The modulation index for an $A.M.$ wave having maximum and minimum peak-to-peak voltages of $14\,mV$ and $6\,mV$ respectively is:

$A$ modulating signal is a square wave,as shown in the figure. If the carrier wave is given as $c(t) = 2 \sin(8 \pi t)$ volts,the modulation index is:

The refractive index of the ionosphere: