For commercial telephonic communication,the frequency range adequate for speech signals is

The maximum amplitude of an $AM$ wave is $90 \ V$ and the minimum amplitude is $10 \ V$. What is the amplitude of the modulating wave in the given $AM$ wave (in $V$)?

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	$IV$. $65-75 \ km$

$A$ 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 $V$)

$A$ 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 $.......... \, V$.

$A$ carrier wave $v_{c}(t) = 160 \sin(2 \pi \times 10^{6} t) \text{ V}$ is made to vary between $V_{\max} = 200 \text{ V}$ and $V_{\min} = 120 \text{ V}$ by a message signal $v_{m}(t) = A_{m} \sin(2 \pi \times 10^{3} t) \text{ V}$. The peak voltage $A_{m}$ of the modulating signal is ..... .