Editing Electromagnetic radiation (section)

== History of discovery ==
{{See also|History of electromagnetic theory|Timeline of electromagnetism and classical optics|Radiation#Discovery}}

Electromagnetic radiation of wavelengths other than those of visible light were discovered in the early 19th century. The discovery of [[infrared]] radiation is ascribed to astronomer [[William Herschel]], who published his results in 1800 before the [[Royal Society of London]].<ref name=HerschelRSIR>{{cite journal|jstor=107057|title=Experiments on the Refrangibility of the Invisible Rays of the Sun. By William Herschel, LL. D. F. R. S|first=William|last=Herschel|date=1 January 1800|journal=Philosophical Transactions of the Royal Society of London|volume=90|pages=284–292|doi=10.1098/rstl.1800.0015|bibcode=1800RSPT...90..284H|doi-access=free}}</ref> Herschel used a glass [[Triangular prism (optics)|prism]] to [[refract]] light from the [[Sun]] and detected invisible rays that caused heating beyond the red part of the spectrum, through an increase in the temperature recorded with a [[thermometer]]. These "calorific rays" were later termed infrared.<ref>{{Cite journal|last1=Holzer|first1=Aton M.|last2=Elmets|first2=Craig A.|date=2010|title=The Other End of the Rainbow: Infrared and Skin|journal=The Journal of Investigative Dermatology|volume=130|issue=6|pages=1496–1499|doi=10.1038/jid.2010.79|issn=0022-202X|pmc=2926798|pmid=20463675}}</ref>

In 1801 German physicist [[Johann Wilhelm Ritter]] discovered [[ultraviolet]] in an experiment similar to Herschel's, using sunlight and a glass prism. Ritter noted that invisible rays near the violet edge of a solar spectrum dispersed by a triangular prism darkened [[silver chloride]] preparations more quickly than did the nearby violet light. Ritter's experiments were an early precursor to what would become photography. Ritter noted that the ultraviolet rays (which at first were called "chemical rays") were capable of causing chemical reactions.<ref>{{Cite web|title=Ultraviolet {{!}} COSMOS|url=https://astronomy.swin.edu.au/cosmos/U/Ultraviolet|url-status=live|archive-url=https://web.archive.org/web/20210301192020/https://astronomy.swin.edu.au/cosmos/u/ultraviolet|archive-date=1 March 2021|access-date=29 September 2021|website=astronomy.swin.edu.au}}</ref><ref>{{Cite journal|last=Davidson|first=Michael W.|date=March 2014|title=Pioneers in Optics: Johann Wilhelm Ritter and Ernest Rutherford|journal=Microscopy Today|language=en|volume=22|issue=2|pages=48–51|doi=10.1017/S1551929514000029|s2cid=135584871|issn=1551-9295|doi-access=free}}</ref>

[[File:James Clerk Maxwell sitting.jpg|thumb|upright|[[James Clerk Maxwell]] (1831–1879)]]
In 1862–64 [[James Clerk Maxwell]] developed equations for the electromagnetic field which suggested that waves in the field would travel with a speed that was very close to the known speed of light. Maxwell therefore suggested that visible light (as well as invisible infrared and ultraviolet rays by inference) all consisted of propagating disturbances (or radiation) in the electromagnetic field. Radio waves were first produced deliberately by [[Heinrich Hertz]] in 1887, using electrical circuits calculated to produce oscillations at a much lower frequency than that of visible light, following recipes for producing oscillating charges and currents suggested by Maxwell's equations. Hertz also developed ways to detect these waves, and produced and characterized what were later termed [[radio wave]]s and [[microwave]]s.<ref name=Jeans>[[Jeans, James]] (1947) [https://archive.org/stream/growthofphysical029068mbp#page/n11/mode/2up The Growth of Physical Science]. Cambridge University Press</ref>{{rp|286,7}}

[[Wilhelm Röntgen]] discovered and named [[X-rays]]. After experimenting with high voltages applied to an evacuated tube on 8 November 1895, he noticed a fluorescence on a nearby plate of coated glass. In one month, he discovered X-rays' main properties.<ref name=Jeans />{{rp|307}}

The last portion of the EM spectrum to be discovered was associated with [[radioactivity]]. [[Henri Becquerel]] found that [[uranium]] salts caused fogging of an unexposed photographic plate through a covering paper in a manner similar to X-rays, and [[Marie Curie]] discovered that only certain elements gave off these rays of energy, soon discovering the intense radiation of [[radium]]. The radiation from [[pitchblende]] was differentiated into alpha rays ([[alpha particle]]s) and beta rays ([[beta particle]]s) by [[Ernest Rutherford]] through simple experimentation in 1899, but these proved to be charged particulate types of radiation. However, in 1900 the French scientist [[Paul Villard]] discovered a third neutrally charged and especially penetrating type of radiation from radium, and after he described it, Rutherford realized it must be yet a third type of radiation, which in 1903 Rutherford named [[gamma ray]]s.

In 1910 British physicist [[William Henry Bragg]] demonstrated that gamma rays are electromagnetic radiation, not particles, and in 1914 Rutherford and [[Edward Andrade]] measured their wavelengths, finding that they were similar to X-rays but with shorter wavelengths and higher frequency, although a 'cross-over' between X and gamma rays makes it possible to have X-rays with a higher energy (and hence shorter wavelength) than gamma rays and vice versa. The origin of the ray differentiates them, gamma rays tend to be natural phenomena originating from the unstable nucleus of an atom and X-rays are electrically generated (and hence man-made) unless they are as a result of [[bremsstrahlung]] X-radiation caused by the interaction of fast moving particles (such as beta particles) colliding with certain materials, usually of higher atomic numbers.<ref name="Jeans" />{{rp|308,9}}