$A$ $TV$ tower has a height of $160 \,m$. Its coverage range is nearly (Earth's radius,$R_e = 6400 \,km$):

$A$ carrier wave of peak voltage $60 \,V$ is used to transmit a message signal. Then the peak voltage of the modulating signal in order to have a modulation index of $90 \%$ is (in $\,V$)

Which type of propagation is used to transmit radio waves from one place to another?

The frequency of a $FM$ transmitter without signal input is called

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

List-$I$ (Layer of atmosphere)	List-$II$ (Approximate height over earth's surface)
$(A)$ $F_1$-Layer	$(I)$ $10\,km$
$(B)$ $D$-Layer	$(II)$ $170-190\,km$
$(C)$ Troposphere	$(III)$ $100\,km$
$(D)$ $E$-Layer	$(IV)$ $65-75\,km$

Choose the correct answer from the options given below:

$A$ 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 ..... .