If in an amplitude modulated wave,the maximum amplitude is $14 \ V$ and the modulation index is $0.4$,then the amplitude of the carrier wave is (in $V$)

Assertion $(A)$: Television signals are received through sky-wave propagation.
Reason $(R)$: The ionosphere reflects electromagnetic waves of frequencies in the range $(3-30)$ $MHz$.
Choose the correct option.

Television signals on earth cannot be received at distances greater than $100\, km$ from the transmission station. The reason behind this is that

If a signal of frequency $3 \ kHz$ is to be transmitted via amplitude modulation,which of the following should be chosen as the carrier wave frequency?

What is the minimum height of an antenna required to transmit a radio signal of frequency $20 \text{ MHz}$?

In $TV$ transmission,the audio signal is ........ modulated and the video signal is ........ modulated.