Editing Polarization (waves) (section)

=== Coordinate frame ===
Regardless of whether polarization state is represented using geometric parameters or Jones vectors, implicit in the parameterization is the orientation of the coordinate frame. This permits a degree of freedom, namely rotation about the propagation direction. When considering light that is propagating parallel to the surface of the Earth, the terms "horizontal" and "vertical" polarization are often used, with the former being associated with the first component of the Jones vector, or zero azimuth angle. On the other hand, in [[astronomy]] the [[equatorial coordinate system]] is generally used instead, with the zero azimuth (or position angle, as it is more commonly called in astronomy to avoid confusion with the [[horizontal coordinate system]]) corresponding to due north.

==== ''s'' and ''p'' designations{{anchor|s and p}} ====
{{see also|Fresnel equations#S and P polarizations}}

[[File:E xy deformation.webm|thumb|upright=1.2|Electromagnetic vectors for {{math|'''E'''}}, {{math|'''B'''}}, and {{math|'''k'''}} with {{math|1='''E''' = '''E'''(''x'',''y'')}} along with 3 planar projections and a deformation surface of total electric field. The light is always ''s''-polarized in the {{mvar|xy}}-plane. {{mvar|θ}} is the polar angle of {{math|'''k'''}} and {{math|''φ''{{sub|'''E'''}}}} is the azimuthal angle of {{math|'''E'''}}.]]

Another coordinate system frequently used relates to the ''[[plane of incidence]]''. This is the plane made by the incoming propagation direction and the vector perpendicular to the plane of an interface, in other words, the plane in which the ray travels before and after reflection or refraction. <!--The rays in this plane are illustrated in the diagram to the right.--> The component of the electric field parallel to this plane is termed ''p-like'' (parallel) and the component perpendicular to this plane is termed ''s-like'' (from {{lang|de|senkrecht}}, German for 'perpendicular'). Polarized light with its electric field along the plane of incidence is thus denoted ''{{dfn|p-polarized}}'', while light whose electric field is normal to the plane of incidence is called ''{{dfn|s-polarized}}''. ''P''-polarization is commonly referred to as ''transverse-magnetic'' (TM), and has also been termed ''pi-polarized'' or ''{{pi}}-polarized'', or ''tangential plane polarized''. ''S''-polarization is also called ''transverse-electric'' (TE), as well as ''sigma-polarized'' or ''σ-polarized'', or ''sagittal plane polarized''.