# (i) Define modulation index. (ii) Why is the amplitude of modulating signal kept less than the amplitude of carrier wave?

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(i) Define modulation index.

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

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(i) Modulation index is a measure of  extent of modulation done on a carrier signal. In Amplitude modulation, it is defined as the ratio of the amplitude of modulating signal to that of the carrier signal.

$m = \frac{A_m}{A_c}$

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