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Wave Optics

Question
CBSEENPH12039108
Wired Faculty App

(i) Define modulation index.

(ii) Why is the amplitude of modulating signal kept less than the amplitude of carrier wave?

Solution

i) The ratio of the amplitude of modulating signal (Em) to the amplitude of carrier wave (Ec) is known as the modulation index of an amplitude modulated wave or amplitude modulation index.

Mathematically it is given by, 
m subscript a space equals space E subscript m over E subscript c

For a modulated wave, we have 
m subscript a space equals space fraction numerator E subscript m a x end subscript minus E subscript m i n end subscript over denominator E subscript m a x end subscript plus E subscript m i n end subscript end fraction E subscript m space less than space E subscript c

ii) Keeping the amplitude of modulating signal less than the amplitude of carrier wave helps one to reduce the distortions in the signal.

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