$A$ transmitting antenna is at a height of $50 \ m$ and the receiving antenna is at a height of $5 \ m$. What is the maximum communication range in $km$? (Take $R = 6400 \ km$)

Mean optical power launched into an $8 \ km$ fibre is $120 \ \mu W$ and mean output power is $4 \ \mu W$,then the overall attenuation is ....... $dB$ (Given $\log 30 = 1.477$)

Match List-$I$ with List-$II$:

List-$I$	List-$II$
$A$. Television signal	$I$. $03\,KHz$
$B$. Radio signal	$II$. $20\,KHz$
$C$. High Quality Music	$III$. $02\,MHz$
$D$. Human speech	$IV$. $06\,MHz$

Choose the correct answer from the options given below:

An oscillator is producing $FM$ waves of frequency $2 \text{ kHz}$ with a frequency variation of $10 \text{ kHz}$. What is the modulation index?

The height of a $TV$ tower is $150 \ m$. If the population density in the area covered by the $TV$ tower is $50 \ \text{lakhs}$, then the population density around the $TV$ tower is ....... $km^{-2}$. (Radius of the Earth is $6.4 \times 10^{6} \ m$)

$A$ basic communication system consists of:
$(a)$ Transmitter
$(b)$ Information source
$(c)$ User of information
$(d)$ Channel
$(e)$ Receiver
The correct sequence of the arrangement is: