The maximum amplitude of an $AM$ wave is $90 \ V$ and the minimum amplitude is $10 \ V$. What is the modulation index of the $AM$ wave in percentage?

$A$ 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 ..... .

In amplitude modulation,the sinusoidal carrier frequency is denoted by $\omega_c$ and the signal frequency is denoted by $\omega_m$. The bandwidth of the signal is such that $\omega_m << \omega_c$. Which of the following frequencies is not contained in the modulated wave?

If multiple waves with modulation indices $n_1, n_2, n_3, ...$ modulate a carrier wave,what is the total modulation index of the resulting wave?

$A$ transmitting antenna has a height of $20 \,m$. What will be the height of the receiving antenna if the maximum distance between them for satisfactory communication in line-of-sight $(LOS)$ mode is $40 \,km$ (in $\,m$)? (The radius of the Earth is $6400 \,km$.)

The government has divided the frequency range from $30\ MHz$ to $60\ MHz$ between $20$ stations,which are independently beaming their signals. Which of the signals can be beamed by each of the stations?