The attenuation in optical fibre is mainly due to

The maximum amplitude of an $AM$ wave is found to be $20 \,V$ while its minimum amplitude is $4 \,V$. The modulation index is

Which of the following is $NOT$ a reason for why we need modulation in communication systems?

$A$ carrier wave of peak voltage $15 V$ 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 $80\%$ (in $V$)?

If the amplitude of the modulated wave and the amplitude of the signal are equal, then the modulation index is .....$\%$

An amplitude modulated signal consists of a message signal of frequency $1 \text{ kHz}$ and peak voltage of $5 \text{ V}$,modulating a carrier frequency of $1 \text{ MHz}$ and peak voltage of $15 \text{ V}$. The correct description of this signal is