Answer:
Step-by-step explanation:
They undergo a wave interference which can either be constructive or destructive interference. Constructive interference happens when the crests of one wave overlap the crests of the other wave (the waves are said to be in phase). This causes an increase in wave amplitude.
Destructive interference occurs when the crests of one wave overlap the troughs of the other wave (waves are said to be out of phase). This causes a decrease in wave amplitude.