Constructive & Destructive

[WYacob_2C]

Can someone explain the difference between constructive and destructive interference, and how larger waves are created in constructive interference while smaller waves are created through destructive.

[Adrianh72]

With constructive interference, the waves are in phase with each other, so you can think of it as being aligned. I like to think of it in terms of "positive" and "negative". Since they are aligned, the positive (parts above the axis) interact with the positive of the other wave and, so the wave gets bigger. During destructive interference, the positive of one interacts with the negative (parts below axis) of the other, so the wave gets smaller. Hopefully this diagram helps too.

constructiveanddestructiveinterference.png (10.71 KiB) Viewed 146 times

[Katherine Chhen 3I]

For destructive interference, would it be possible for the two waves to be equal to each other so that they cancel out or does the “negative” have to be smaller than the “positive” wave?

[GFolk_1D]

Yes this is possible. However, they would have to have the exact same wavelength and frequency.

[Robert Cross 1A]

For destructive interference, would it be possible for the two waves to be equal to each other so that they cancel out or does the “negative” have to be smaller than the “positive” wave?

Yes. A good real life example that helped me better conceptualize this can be found in how noise-cancelling headphones operate. They essentially have microphones in the headphones which amplify the opposite waveform of ambient environmental noise of the same amplitude through the speakers, resulting in the ambient audio waves cancelling with the internally-produced waves of the headphone speakers. In reality, it's not 100% cancellation, but that's the basic idea behind their function.