Editing Ultraviolet (section)

== History and discovery ==
"Ultraviolet" means "beyond violet" (from [[Latin]] ''ultra'', "beyond"), violet being the color of the highest frequencies of [[visible light]]. Ultraviolet has a higher frequency (thus a shorter wavelength) than violet light.

UV radiation was discovered in February 1801 when the German physicist [[Johann Wilhelm Ritter]] observed that invisible rays just beyond the violet end of the visible spectrum darkened [[silver chloride]]-soaked paper more quickly than violet light itself. He announced the discovery in a very brief letter to the [[Annalen der Physik]]<ref>{{Cite web |last=Gbur |first=Gregory |author-link=Greg Gbur |date=2024-07-25 |title=The discovery of ultraviolet light |url=https://skullsinthestars.com/2024/07/24/the-discovery-of-ultraviolet-light/ |access-date=2024-09-17 |website=Skulls in the Stars |language=en}} citing to {{cite journal |title=Von den Herren Ritter und Böckmann |lang=de |trans-title=From Misters Ritter and Böckmann |journal=[[Annalen der Physik]] |year=1801 |volume=7 |issue=4 |page=527 |url=https://archive.org/details/sim_annalen-der-physik_1801_7}}</ref><ref name=Frercks2009>{{Cite journal |last1=Frercks |first1=Jan |last2=Weber |first2=Heiko |last3=Wiesenfeldt |first3=Gerhard |date=2009-06-01 |title=Reception and discovery: the nature of Johann Wilhelm Ritter's invisible rays |url=https://linkinghub.elsevier.com/retrieve/pii/S003936810900020X |journal=Studies in History and Philosophy of Science Part A |volume=40 |issue=2 |pages=143–156 |doi=10.1016/j.shpsa.2009.03.014 |bibcode=2009SHPSA..40..143F |issn=0039-3681|url-access=subscription }}</ref> and later called them "(de-)oxidizing rays" ({{langx|de|de-oxidierende Strahlen}}) to emphasize [[chemical reactivity]] and to distinguish them from "[[Infrared|heat rays]]", discovered the previous year at the other end of the visible spectrum. The simpler term "chemical rays" was adopted soon afterwards, and remained popular throughout the 19th century, although some said that this radiation was entirely different from light (notably [[John William Draper]], who named them "tithonic rays"<ref>{{cite journal |last=Draper |first=J.W. |author-link=John William Draper |year=1842 |title=On a new Imponderable Substance and on a Class of Chemical Rays analogous to the rays of Dark Heat |url=https://books.google.com/books?id=7XiUObxbsYQC&pg=RA2-PA453 |journal=[[The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science]] |volume=80 |pages=453–461}}</ref><ref>{{Cite journal |last=Draper |first=John W. |date=1843 |title=Description of the tithonometer, an instrument for measuring the chemical force of the indigo-tithonic rays |url=https://books.google.com/books?id=DuDij5b_hJ4C&pg=PA401 |journal=[[The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science]] |language=en |volume=23 |issue=154 |pages=401–415 |doi=10.1080/14786444308644763 |issn=1941-5966}}</ref>). The terms "chemical rays" and "heat rays" were eventually dropped in favor of ultraviolet and [[infrared]] [[radiation]], respectively.<ref>{{cite book|last1=Beeson|first1=Steven|last2=Mayer|first2=James W|title=Patterns of light: chasing the spectrum from Aristotle to LEDs|publisher=Springer|location=New York|isbn=978-0-387-75107-8|page=149|chapter=12.2.2 Discoveries beyond the visible|date=2007-10-23}}</ref><ref name="hockberger">
{{Cite journal
 | last = Hockberger
 | first = Philip E.
 | title = A history of ultraviolet photobiology for humans, animals and microorganisms
 | journal = [[Photochem. Photobiol.]]
 | volume = 76
 | issue = 6
 | pages = 561–79
 | date = December 2002
 | doi = 10.1562/0031-8655(2002)0760561AHOUPF2.0.CO2
 | pmid = 12511035
 | s2cid = 222100404
 }}</ref> In 1878, the sterilizing effect of short-wavelength light by killing bacteria was discovered. By 1903, the most effective wavelengths were known to be around 250&nbsp;nm. In 1960, the effect of ultraviolet radiation on DNA was established.<ref>{{cite book |first1=James |last1=Bolton |first2=Christine |last2=Colton |title=The Ultraviolet Disinfection Handbook |publisher=American Water Works Association |year=2008 |isbn=978-1 58321-584-5 |pages=3–4}}</ref>

The discovery of the ultraviolet radiation with wavelengths below 200&nbsp;nm, named "vacuum ultraviolet" because it is strongly absorbed by the oxygen in air, was made in 1893 by German physicist [[Victor Schumann]].<ref name="Lyman">The [[ozone layer]] also protects living beings from this.
{{Cite journal
 | last = Lyman
 | first = Theodore
 | author-link = Theodore Lyman IV
 | title = Victor Schumann
 | journal = The Astrophysical Journal
 | volume = 38
 | issue = 1
 | pages = 1–4
 | year = 1914
 | bibcode = 1914ApJ....39....1L
 | doi = 10.1086/142050
 | doi-access = free
 }}</ref> The division of UV into UVA, UVB, and UVC was decided "unanimously" by a committee of the Second International Congress on Light on August 17th, 1932, at the [[Christiansborg Palace|Castle of Christiansborg]] in Copenhagen.<ref>{{Cite journal |last=Coblentz |first=W. W. |date=1932-11-04 |title=The Copenhagen Meeting of the Second International Congress on Light |url=https://www.science.org/doi/10.1126/science.76.1975.412 |journal=Science |language=en |volume=76 |issue=1975 |pages=412–415 |doi=10.1126/science.76.1975.412 |issn=0036-8075}}</ref>