If the highest modulating frequency of the wave is $5\, kHz$,the number of stations that can be accommodated in a $150\, kHz$ bandwidth are

In amplitude modulation,the amplitude of the carrier wave is $10 \ V$ and the amplitude of one of the sidebands is $2 \ V$. Then the modulation index is

The characteristic impedance of a coaxial cable is of the order of .......... $\Omega$.

$A$ $TV$ transmitter has a range of $50 \ km$. The height of the $TV$ transmitter is $......$ (Radius of the earth $R_e = 6.4 \times 10^6 \ m$) (in $m$)

Which of the following is $NOT$ a reason for why we need modulation in communication systems?

$A$ $25\, m$ long antenna is mounted on an antenna tower. The height of the antenna tower is $75\, m$. The wavelength (in meter) of the signal transmitted by this antenna would be