The maximum distance up to which $TV$ transmission from a $TV$ tower of height $h$ can be received is proportional to

In amplitude modulation,the amplitude of the $.......$ wave varies in proportion to the instantaneous value of the $.......$ wave.

$A$ carrier wave of peak voltage $20 V$ is used to transmit a message signal. For getting a modulation index of $60 \%$,the peak voltage of the modulating signal is (in $V$)

If the ratio of the maximum and minimum amplitudes of an amplitude modulated wave is $7:3$,then the modulation index is

Given below in the left column are different modes of communication using the kinds of waves given in the right column.

$A$. Optical Fiber Communication	$P$. Ultrasound
$B$. Radar	$Q$. Infrared Light
$C$. Sonar	$R$. Microwaves
$D$. Mobile Phones	$S$. Radio Waves

From the options given below, find the most appropriate match between entries in the left and the right column.

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