The circuit used to separate information signals from the carrier wave is called a .......

$A$ sinusoidal carrier voltage is amplitude modulated. The resultant amplitude modulated wave has maximum and minimum amplitude of $120 \, V$ and $80 \, V$ respectively. The amplitude of each sideband is $.......... \, V$.

$A$ wave is represented as $e = 10\,(1 + 6\, \sin(50t)) \sin(10^8t)$. The modulation index is:

Long range radio transmission is possible when the radio waves are reflected from the ionosphere. For this to happen,the frequency of the radio waves must be in the range:

$A$ $TV$ transmitting antenna is $98\,m$ high and the receiving antenna is at the ground level. If the radius of the earth is $6400\,km$,the surface area covered by the transmitting antenna is approximately $.........\,km^2$

Match Column $A$ (layers in the ionosphere for skywave propagation) with Column $B$ (their height range).

Column $A$	Column $B$
$A$. $D$-layer	$I$. $250-400 \ km$
$B$. $E$-layer	$II$. $170-190 \ km$
$C$. $F_1$-layer	$III$. $95-120 \ km$
$D$. $F_2$-layer	$IV$. $65-75 \ km$