Wave interference

For interference in radio communications, see Interference (communication).
"Interference pattern" redirects here. For Moiré patterns, see Moiré pattern. For the medical term, see Interference pattern (electromyography).
When two or more waves travel through a medium and superpose then the resultant intensity do not distributed uniformly in the space. At some places, it is maximum while at some other places it is minimum. This non uniform distribution of intensity or energy of light is known as interference.
The interference of two waves. In phase: the two lower waves combine (left panel), resulting in a wave of added amplitude (constructive interference). Out of phase: (here by 180 degrees), the two lower waves combine (right panel), resulting in a wave of zero amplitude (destructive interference).
Interfering water waves on the surface of a lake

In physics, interference is a phenomenon in which two coherent waves are combined by adding their intensities or displacements with due consideration for their phase difference. The resultant wave may have greater intensity (constructive interference) or lower amplitude (destructive interference) if the two waves are in phase or out of phase, respectively. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, surface water waves, gravity waves, or matter waves as well as in loudspeakers as electrical waves.