In this simple case ''M'' is identical to the [[#Modulation Index|modulation index]], discussed below. With ''M''=0.5 the amplitude modulated signal ''y''(''t'') thus corresponds to the top graph (labelled "50% Modulation") in Figure 4.
Using [[Prosthaphaeresis#The identities|prosthaphaeresis identities]], ''y''(''t'') can be shown to be the sum of three sine waves:
Therefore, the modulated signal has three components: the carrier wave ''c(t)'' which is unchanged, and two pure sine waves (known as [[sideband]]s) with frequencies slightly above and below the carrier frequency ''f<sub>c</sub>''.
