This chapter is from the book
Interference
When two waves collide, they can either amplify the signal creating a brighter pulse or interfere with one another. When they are in phase they amplify the signal in a phenomenon called constructive interference.When the signals that are out of phase collide, destructive interference occurs and the signal is weakened (see Figure 3.12).
Figure 3.12 Interference can amplify or diminish a signal.