$A$ carrier wave of peak voltage $12 \, V$ is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of $75 \%$? ...... $V$

Statement-$1$: Sky wave signals are used for long-distance radio communication.
Statement-$2$: These signals are generally less stable than ground wave signals.

In an $AM$ wave,the frequencies of $LSB$ and $USB$ are $2.99 \ MHz$ and $3.01 \ MHz$ respectively. The carrier frequency is ....... and the modulating frequency is .......

$A$ message signal is used to modulate a carrier signal of frequency $5 MHz$ and peak voltage of $40 V$. In the process,two side-bands are produced separated by $40 kHz$. If the modulation index is $0.75$,then the peak voltage and frequency of the message signal,respectively,are:

The radio horizon of the transmission of an antenna placed on the $20^{\text{th}}$ floor in a shopping mall,where the height of each floor is $2 \,m$,is (Radius of Earth is $6.4 \times 10^6 \,m$): (in $\,km$)

The loss of strength of a signal while propagating through a medium is known as