In a frequency modulated wave:

An amplitude modulated wave is represented by $V_{AM} = 10[1 + 0.4 \cos(2 \pi \times 10^4 t)] \cos(2 \pi \times 10^7 t) \text{ V}$. The total bandwidth of the amplitude modulated wave is:

$A$ speech signal of $3 \text{ kHz}$ is used to modulate a carrier signal of frequency $1 \text{ MHz}$ using amplitude modulation. The frequencies of the sidebands will be:

The electron density of the ionospheric layer is $10^{11} \ m^{-3}$. Communication waves of frequency up to $f_c$ $MHz$ will be reflected by the ionospheric layer. Find $f_c$.

For a coaxial cable,the typical repeater spacing is approximately............$km$.

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?