If in an amplitude modulated wave,the maximum amplitude is $14 \ V$ and the modulation index is $0.4$,then the amplitude of the carrier wave is (in $V$)

Three signals related to amplitude modulation are shown in the figure. The correct assignment of the signals is

The heights of the transmitting and receiving antennas are $33.8 \ m$ and $64.8 \ m$ respectively. The maximum distance between the antennas for satisfactory communication in a line of sight mode is (Radius of the earth $= 6400 \ km$) (in $km$)

For $VHF$ signal broadcasting,what is the maximum service area in $km^{2}$ that will be covered by an antenna tower of height $30\, m$,if the receiving antenna is placed at the ground? Let the radius of the earth be $6400\, km$. (Round off to the nearest integer) (Take $\pi$ as $3.14$)

If $E_c$ and $E_m$ are peak values of carrier and modulating signals,respectively,then for $100 \%$ modulation,

What is the advantage of an optical fibre?