What is light modulation?

What is the modulation ? What is need for modulation?

An audio signal of amplitude one-third the carrier amplitude is employed in amplitude modulation. What is the modulation index?

A modulating signal is a square wave, as shown in Fig. 15.14. The carrier wave is given by c(t)=2sin(8 pi t )volts. What is the modulation index? :

What is a modulator ?

What is modulation? What are its types?