The height of an antenna is $500 \ m$. Its range is ........ $km$. (Radius of the Earth is $6400 \ km$)

$AM$ (Amplitude Modulation) is used for broadcasting because...

In $AM$ modulation,a signal is modulated on a carrier wave such that maximum and minimum amplitude are found to be $6\,V$ and $2\,V$ respectively. The modulation index is $\dots \%$.

The sound produced by a tuning fork is a/an .....

The amplitude of $15 \sin (1000 \pi t)$ is modulated by $10 \sin (4 \pi t)$ signal. The amplitude modulated signal contains frequency(ies) of
$A) 500 \text{ Hz}$
$B) 2 \text{ Hz}$
$C) 250 \text{ Hz}$
$D) 498 \text{ Hz}$
$E) 502 \text{ Hz}$
Choose the correct answer from the options given below:

The height of a transmission antenna is $49 \,m$ and that of the receiving antenna is $64 \,m$. What should be the maximum distance between them for line of sight transmission (in $\,km$)?