Interference is the interaction of two or more waves passing the same point. Constructive interference occurs when the waves add in phase, producing a larger peak than any wave alone, whereas destructive interference occurs when waves add out of phase, producing smaller peaks than one of the waves alone.

Constructive Interference, Destructive Interference, Double Slit Interference, Fringe, Interference Pattern, Interferogram, Interferometer, Interferometry, Multiple Slit Interference