Destructive interference

When two waves meet which are in antiphase, their amplitudes add together to create a wave with a smaller amplitude.

This is because, at that point, one wave has a positive displacement, while one has a negative displacement - so they’ll add to make a smaller amplitude.

Thsi is called destructive interference.

If the phase difference between the two waves is \pi or a multiple of 2\pi and offset by \pi, the waves are in phase. That means that the peaks of one wave line up exactly with the troughs of the other wave, and the troughs line up exactly with the peaks.

When this happens, if the waves are the same, they are in antiphase and so the trough is the negative of the peak. That means they will add together to make an amplitude of zero - they cancel out completely.

flashcards

QuestionAnswer
Destructive interferenceWhen two waves that are in antiphase meet, their amplitudes add to create a wave with a smaller amplitude.
What does it mean when two waves are in antiphase?One wave has a positive displacement while the other has a negative displacement; the peaks of one wave line up exactly with the troughs of the other.
What is the phase difference for two identical waves in antiphase?\pi or a multiple of 2\pi offset by \pi.
What happens when two identical waves in antiphase add together?They cancel out completely, creating an amplitude of zero.