Suppose the carrier wave is modulated in accordance with the amplitude of a message signal.
The modulation index is m. The Instantaneous carrier voltage is represented by, ve = Vc sinωet . The instantaneous modulating voltage is presented by, vm = Vm sinωmt . The time variation of the instantaneous voltage, of the amplitude modulated wave, will be represented by,
(1) Ve sinωet
(2) Vm sinωmt
(3) Ve (1+sinωmt)
(4) Ve (1+sinωmt)sinωet