## Constructive and Destructive Interference [ENDORSED]

Amber_Candelaria_1D
Posts: 21
Joined: Sat Jul 09, 2016 3:00 am

### Constructive and Destructive Interference

What does it mean for waves to interact in-phase and out-of-phase?

Julia Nakamura 2D
Posts: 33
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Constructive and Destructive Interference

Two waves are said to be acting in phase, or in constructive interference, when the peak of one wave aligns with the peak of another wave (or the trough of one wave aligns with the trough of another wave). This interaction will create bigger peaks and troughs.

However, two waves act out of phase, or act in destructive interference, when the peak of one wave interacts with the trough of another wave. If these waves are the same size, they may cancel each other out completely. However in the example from the lecture today, the top wave had a larger amplitude than the bottom wave, so it just created a smaller wave.

Hope this helps!

Omer Lavian 2K
Posts: 44
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Constructive and Destructive Interference  [ENDORSED]

Imagine two sine waves (sort of like the waves Dr. Lavelle has drawn for us in class) of the same wavelength, frequency, and amplitude (distance from the equilibrium position, the point between the peak and the trough, to either a peak or a trough). If the peaks of one wave line up with the peaks of the other, and the troughs of one wave line up with the troughs of the other, then the waves are in phase, and the amplitudes of the two waves add up, resulting in a wave with double the amplitude of either of the original waves. However, if the peaks of one wave line up with the troughs of the other and vice versa, then the effects of the waves cancel each other out (This is roughly how noise canceling headphones work. See this video for more information: https://www.youtube.com/watch?v=VTx4JgYsW5s)

Banik_Housepian_2K
Posts: 39
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Constructive and Destructive Interference

what if the waves are neither lined up trough to peak, peak to peak, or trough to trough, and are rather lined up somewhere in the middle. then are they constructive or destructive? how does this work out?