Editing Wave (section)

=== Standing waves ===
{{Main|Standing wave|Acoustic resonance|Helmholtz resonance|Organ pipe}}

[[File:Standing wave.gif|class=skin-invert-image|thumb|right|300px|Standing wave. The red dots represent the wave [[Node (physics)|nodes]].]]

A standing wave, also known as a ''stationary wave'', is a wave whose [[Envelope (waves)|envelope]] remains in a constant position. This phenomenon arises as a result of [[Interference (wave propagation)|interference]] between two waves traveling in opposite directions.

The ''sum'' of two counter-propagating waves (of equal amplitude and frequency) creates a ''standing wave''. Standing waves commonly arise when a boundary blocks further propagation of the wave, thus causing wave reflection, and therefore introducing a counter-propagating wave. For example, when a [[violin]] string is displaced, transverse waves propagate out to where the string is held in place at the [[Bridge (instrument)|bridge]] and the [[Nut (string instrument)|nut]], where the waves are reflected back. At the bridge and nut, the two opposed waves are in [[antiphase]] and cancel each other, producing a [[node (physics)|node]]. Halfway between two nodes there is an [[antinode]], where the two counter-propagating waves ''enhance'' each other maximally. There is no net [[Energy transfer|propagation of energy]] over time.

<gallery>
Image:Standing waves on a string.gif|One-dimensional standing waves; the [[fundamental frequency|fundamental]] mode and the first 5 [[overtone]]s
Image:Drum vibration mode01.gif|A two-dimensional [[Vibrations of a circular drum|standing wave on a disk]]; this is the fundamental mode.
Image:Drum vibration mode21.gif|A [[Vibrations of a circular drum|standing wave on a disk]] with two nodal lines crossing at the center; this is an overtone.
</gallery>