when modulation index is kept less than 1 distortion dosent occur.......how and why???? plxzzzzzzz reply briefly........nd fastly.......

Modulation index in amplitude modulation is the ratio of voltage of modulating wave to the voltage of carrier wave. As the low frequency modulating signal is enveloped with a high frequency carrier wave so the distortion is restricted due to the high frequency carrier wave for modulation index lying between 0 and 1. If amplitude of modulating wave is greater than the carrier wave then the carrier wave gets over-modulated.This over-modulation results in distorted waveform envelope which will result in a distorted output signal.