Editing Photon (section)

=== Polarization and spin angular momentum ===
{{main|Photon polarization|Spin angular momentum of light}}
The photon also carries [[Spin angular momentum of light|spin angular momentum]], which is related to [[photon polarization]]. (Beams of light also exhibit properties described as [[orbital angular momentum of light]]).

The angular momentum of the photon has two possible values, either {{mvar|+ħ}} or {{mvar|−ħ}}. These two possible values correspond to the two possible pure states of [[circular polarization]]. Collections of photons in a light beam may have mixtures of these two values; a linearly polarized light beam will act as if it were composed of equal numbers of the two possible angular momenta.<ref name="Hecht">{{Cite book |last=Hecht |first=Eugene |title=Optics |date=1998 |publisher=Addison-Wesley |isbn=978-0-201-83887-9 |edition=3rd |location=Reading, Massachusetts; Harlow |language=en-us}}</ref>{{rp|325}}

The spin angular momentum of light does not depend on its frequency, and was experimentally verified by [[C. V. Raman]] and S. Bhagavantam in 1931.<ref name="spin">{{Cite journal |last1=Raman |first1=C. V. |author1-link=C. V. Raman |last2=Bhagavantam |first2=S. |year=1931 |title=Experimental proof of the spin of the photon |url=http://dspace.rri.res.in/bitstream/2289/2123/1/1931%20IJP%20V6%20p353.pdf |url-status=dead |journal=Indian Journal of Physics |volume=6 |issue=3244 |page=353 |bibcode=1932Natur.129...22R |doi=10.1038/129022a0 |s2cid=4064852 |archive-url=https://web.archive.org/web/20160603235132/http://dspace.rri.res.in/bitstream/2289/2123/1/1931%20IJP%20V6%20p353.pdf |archive-date=2016-06-03 |access-date=2008-12-28 |hdl-access=free |hdl=10821/664}}</ref>