Interference

1. Constructive Interference: When waves collide/crash into each other and form a larger wave. The peaks of both waves line up with each other so they add together to make a larger wave.

2. Destructive Interference: When waves collide and interfere with each other so they cancel out. The crests of one wave line up with the troughs of the other wave so they cancel each other and the wave ends up like a straight line.