In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude.

- Wave interferenceThis phenomenon arises as a result of interference between two waves traveling in opposite directions.

- Wave4 related topics

## Quantum mechanics

Fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles.

Fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles.

Quantum mechanics differs from classical physics in that energy, momentum, angular momentum, and other quantities of a bound system are restricted to discrete values (quantization), objects have characteristics of both particles and waves (wave–particle duality), and there are limits to how accurately the value of a physical quantity can be predicted prior to its measurement, given a complete set of initial conditions (the uncertainty principle).

Another consequence of the mathematical rules of quantum mechanics is the phenomenon of quantum interference, which is often illustrated with the double-slit experiment.

## Wavelength

Spatial period of a periodic wave—the distance over which the wave's shape repeats.

Spatial period of a periodic wave—the distance over which the wave's shape repeats.

The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.

Sinusoids are the simplest traveling wave solutions, and more complex solutions can be built up by superposition.

## Crest and trough

A crest point on a wave is the maximum value of upward displacement within a cycle.

When the crests and troughs of two sine waves of equal amplitude and frequency intersect or collide, while being in phase with each other, the result is called constructive interference and the magnitudes double (above and below the line).

## Superposition principle

Sum of the responses that would have been caused by each stimulus individually.

Sum of the responses that would have been caused by each stimulus individually.

Fourier analysis is particularly common for waves.

The phenomenon of interference between waves is based on this idea.