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In electrodynamics, the strength and direction of an electric field is defined by its electric field vector. In the case of a circularly polarized wave, as seen in the accompanying animation, the tip of the electric field [[Euclidean vector|vector]], at a given point in space, relates to the phase of the light as it travels through time and space. At any instant of time, the electric field vector of the wave indicates a point on a [[helix]] oriented along the direction of propagation. A circularly polarized wave can rotate in one of two possible senses: clockwise or ''right-handed circular polarization (RHCP)'' in which the electric field vector rotates in a [[Right-hand rule|right-hand]] sense with respect to the direction of propagation, and counter-clockwise or ''left-handed circular polarization (LHCP)'' in which the vector rotates in a [[left hand rule|left-hand]] sense.
''Circular polarization'' is a [[limiting case (mathematics)|limiting case]] of ''[[elliptical polarization]]''. The other [[special case]] is the easier-to-understand ''[[linear polarization]]''. All three terms were coined by [[Augustin-Jean Fresnel]], in a memoir read to the [[French Academy of Sciences]] on 9 December 1822.<ref name=fresnel-1822z>A. Fresnel, "Mémoire sur la double réfraction que les rayons lumineux éprouvent en traversant les aiguilles de cristal de roche suivant les directions parallèles à l'axe", read 9 December 1822; printed in H. de Senarmont, E. Verdet, and L. Fresnel (eds.), ''Oeuvres complètes d'Augustin Fresnel'', vol. 1 (1866), pp.{{nnbsp}}731–51; translated as "Memoir on the double refraction that light rays undergo in traversing the needles of quartz in the directions parallel to the axis", {{Zenodo|4745976}}, 2021 (open access); §§9–10.</ref><ref>
The phenomenon of polarization arises as a consequence of the fact that [[light]] behaves as a two-dimensional [[Transverse wave#Explanation|transverse wave]].
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To avoid confusion, it is good practice to specify "as defined from the point of view of the source" or "as defined from the point of view of the receiver" when discussing polarization matters.
The archive of the [https://web.archive.org/web/20090822015912/http://www.its.bldrdoc.gov/fs-1037/ US Federal Standard 1037C] proposes two contradictory conventions of handedness.<ref>In one ___location it is stated..."Note 1. ... In general, the figure, i.e., polarization, is elliptical and is traced in a clockwise or anti-clockwise sense, as viewed in the direction of propagation. ... Rotation of the electric vector in a clockwise sense is designated right-hand polarization, and rotation in an anti-clockwise sense is designated left-hand polarization. "[http://www.its.bldrdoc.gov/fs-1037//dir-028/_4059.htm] {{Webarchive|url=https://web.archive.org/web/20110514080812/http://www.its.bldrdoc.gov/fs-1037/dir-028/_4059.htm |date=2011-05-14 }} In another ___location it is stated... "Note 4: Circular polarization may be referred to as "right-hand" or "left-hand
== FM radio ==
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