Amplitude modulation (AM)

Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent.  

Or 

In case of AM amplitude of higher frequency carrier signet is varied with respect to base bond signal.

Mat lab Code 

clear all;

close all;

F=10;

Fs=200*F;

Fc=100;

t=0:1/Fs:1/F;

k=0.5;

m=sin(2*pi*F*t);

Ac=1;  

s=[Ac+m*k].*cos(2*pi*Fc*t);

c=Ac*cos(2*pi*Fc*t);

subplot(4,2,1);

plot(t,m);

subplot(4,2,2);

plot(t,c);

subplot(4,2,3);

plot(t,s);

Output: