Editing Wave vector (section)

{{Short description|Vector describing a wave; often its propagation direction}}
{{Use American English|date=January 2019}}

In [[physics]], a '''wave vector''' (or '''wavevector''') is a [[vector (geometric)|vector]] used in describing a [[wave]], with a typical unit being cycle per metre. It has a [[Euclidean vector|magnitude and direction]]. Its magnitude is the [[wavenumber]] of the wave (inversely proportional to the [[wavelength]]), and its direction is perpendicular to the [[wavefront]].  In isotropic media, this is also the direction of [[wave propagation]].

A closely related vector is the '''angular wave vector''' (or '''angular wavevector'''), with a typical unit being radian per metre.  The wave vector and angular wave vector are related by a fixed constant of proportionality, 2{{pi}}&nbsp;radians per cycle.

It is common in several fields of [[physics]] to refer to the angular wave vector simply as the ''wave vector'', in contrast to, for example, [[crystallography]].<ref>Physics example: {{cite book| url=https://books.google.com/books?id=c60mCxGRMR8C&pg=PA288 | title= Handbook of Physics| author= Harris, Benenson, Stöcker|page=288| isbn=978-0-387-95269-7| year=2002}}</ref><ref>Crystallography example: {{cite book| url=https://books.google.com/books?id=xjIGV_hPiysC&pg=PA259 | title=Modern Crystallography |author=Vaĭnshteĭn| page=259| isbn=978-3-540-56558-1| year=1994}}</ref>  It is also common to use the symbol {{mvar|'''k'''}} for whichever is in use.

In the context of [[special relativity]], a ''[[wave four-vector]]'' can be defined, combining the (angular) wave vector and (angular) frequency.