Editing Plane wave (section)

===Traveling plane wave===
[[File:Plane wave wavefronts 3D.svg|thumb|right|300px|The [[wavefront]]s of a plane wave traveling in [[3-space]]]]

Often the term "plane wave" refers specifically to a ''[[traveling plane wave]]'', whose evolution in time can be described as simple translation of the field at a constant ''[[Phase velocity|wave speed]]'' <math>c</math> along the direction perpendicular to the wavefronts.  Such a field can be written as  
<math display="block">F(\vec x, t) = G\left(\vec x \cdot \vec n - c t\right)\,</math>
where <math>G(u)</math> is now a function of a single real parameter <math>u = d - c t</math>, that describes the "profile" of the wave, namely the value of the field at time <math>t = 0</math>, for each displacement <math>d = \vec x \cdot \vec n</math>.  In that case, <math>\vec n</math> is called the ''[[direction of propagation]]''. For each displacement <math>d</math>, the moving plane perpendicular to <math>\vec n</math> at distance <math>d + c t</math> from the origin is called a  "[[wavefront]]".  This plane travels along the direction of propagation <math>\vec n</math> with velocity <math>c</math>; and the value of the field is then the same, and constant in time, at every one of its points.<ref>{{cite book |last=Jackson |first= John David |author-link= John David Jackson (physicist) |date= 1998 |title=[[Classical Electrodynamics (book)|Classical Electrodynamics]] |location=New York |publisher=[[Wiley (publisher)|Wiley]] |isbn= 9780471309321 |edition=3 |page = 296}}</ref>