Define the terms ‘modulation Index' for an AM wave. What would be the modulation Index for an AM wave for which the maximum amplitude Is $\text{'}a\text{'}$ and the minimum amplitude Is $\text{'}b\text{'}$?

Write briefly any two factors which demonstrate the need for modulating a signal. Draw a suitable diagram to show amplitude modulation using sinusoidal signal as the modulating signal.

Which mode of wave propagation is suitable for television broadcast and satellite communication and why ? Draw a suitable diagram depicting this mode of propagation of the wave.

A TV tower is $80 \mathrm{m}$ tall. Calculate the maximum distance upto which the signal transmitted from the tower can be received.

Write two factors justifying the need of modulation for transmission of an audio signal.