Interference

Interference is the result of adding two or more waves. Where the waves meet, their values are summed point by point.

• Constructive interference: peaks meet peaks, so the combined wave is larger.
• Destructive interference: peaks meet troughs, so the combined wave is smaller. When a wave meets its exact inverse the sum is flat: full cancellation.

Two sine waves interfere according to their phase difference; at 180° they cancel completely.