The transmission loss per kilometer in an optical fiber is approximately...........$dB$.

$A$ $T$.$V$. tower has a height of $100 \, m$. The average population density around the tower is $1000 \, km^{-2}$ and the radius of the earth is $6.37 \times 10^6 \, m$. The population covered is

In an $AM$ wave,the total power is $900 \ W$. For $100\%$ modulation,the power transmitted in the sidebands is ... $W$.

If a radio receiver amplifies all frequency signals equally and well,it is said to have high . . . . . . .

In an amplitude modulated wave for an audio frequency of $500 \, \text{cycles/second}$, the appropriate carrier frequency will be ........ $\text{cycles/second}$.

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	$IV$. $65-75 \ km$