Editing C. V. Raman (section)

==== Background ====

Raman's second important discovery on the scattering of light was a new type of radiation, an eponymous phenomenon called the Raman effect.<ref name="Singh-2018" /> After discovering the nature of light scattering that caused blue colour of water, he focused on the principle behind the phenomenon. His experiments in 1923 showed the possibility of other light rays formed in addition to the [[incident ray]] when sunlight was filtered through a violet glass in certain liquids and solids. Ramanathan believed that this was a case of a "trace of [[fluorescence]]."<ref name="Mukherji-2018b" /> In 1925, [[K. S. Krishnan]], a new Research Associate, noted the theoretical background for the existence of an additional scattering line beside the usual polarised elastic scattering when light scatters through liquid.<ref>{{Cite journal|last=Krishnan|first=K.S.|date=1925|title=LXXV. On the molecular scattering of light in liquids|journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science|language=en|volume=50|issue=298|pages=697–715|doi=10.1080/14786442508634789}}</ref> He referred to the phenomenon as "feeble fluorescence."<ref>{{Cite journal|last=Mallik|first=D. C. V.|date=2000|title=The Raman effect and Krishnan's diary|url=https://royalsocietypublishing.org/doi/10.1098/rsnr.2000.0097|journal=Notes and Records of the Royal Society of London|language=en|volume=54|issue=1|pages=67–83|doi=10.1098/rsnr.2000.0097|s2cid=143485844|access-date=13 December 2020|archive-date=24 October 2019|archive-url=https://web.archive.org/web/20191024125416/https://royalsocietypublishing.org/doi/10.1098/rsnr.2000.0097|url-status=live|url-access=subscription}}</ref> But the theoretical attempts to justify the phenomenon were quite futile for the next two years.<ref>{{Cite journal|last1=Raman|first1=C.V.|last2=Krishnan|first2=K.S.|date=1927|title=Magnetic double-refraction in liquids. part I.—benzene and its derivatives|journal=Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character|language=en|volume=113|issue=765|pages=511–519|doi=10.1098/rspa.1927.0004|bibcode=1927RSPSA.113..511R|doi-access=free}}</ref>

The major impetus was the discovery of [[Compton scattering|Compton effect]]. [[Arthur Compton]] at [[Washington University in St. Louis]] had found evidence in 1923 that [[electromagnetic waves]] can also be described as particles.<ref name="Compton effect">{{cite journal|author=Compton, Arthur H.|date=May 1923|title=A Quantum Theory of the Scattering of X-Rays by Light Elements|journal=[[Physical Review]]|volume=21|issue=5|pages=483–502|bibcode=1923PhRv...21..483C|doi=10.1103/PhysRev.21.483|doi-access=free}}</ref> By 1927, the phenomenon was widely accepted by scientists, including Raman.<ref>{{Cite journal|last=Raman|first=C. V.|date=1927|title=Thermodynamics, Wave-theory, and the Compton Effect|journal=Nature|language=en|volume=120|issue=3035|pages=950–951|doi=10.1038/120950a0|bibcode=1927Natur.120..950R|s2cid=29489622}}</ref> As the news of Compton's [[Nobel Prize in Physics]] was announced in December 1927, Raman ecstatically told Krishnan, saying:

{{blockquote|Excellent news... very nice indeed. But look here Krishnan. If this is true of X-Rays, it must be true of Light too. I have always thought so. There must be an Optical analogue to Compton Effect. We must pursue it and we are on the right lines. It must and shall be found. The Nobel Prize must be won.<ref name="Ramdas-1973">{{Cite journal|last=Ramdas|first=L. A.|date=1973|title=Dr. C. V. Raman (1888–1970), Part II|url=http://dspace.rri.res.in:8080/jspui/handle/2289/6371|journal=Journal of Physics Education|language=en|volume=1|issue=2|pages=2–18|access-date=12 March 2020|archive-date=31 October 2020|archive-url=https://web.archive.org/web/20201031071756/http://dspace.rri.res.in:8080/jspui/handle/2289/6371|url-status=live}}</ref> }}But the origin of the inspiration went further. As Compton later recollected "that it was probably the Toronto debate that led him to discover the Raman effect two years later."<ref name="Banerjee-2014" /> The Toronto debate was about the discussion on the existence of light quantum at the [[British Science Association|British Association for the Advancement of Science]] meeting held at Toronto in 1924. There Compton presented his experimental findings, which [[William Duane (physicist)|William Duane]] of [[Harvard University]] argued with his own with evidence that light was a wave.<ref>{{Cite journal|last=Singh|first=Rajinder|date=2002|title=C. V. Raman and the Discovery of the Raman Effect|journal=Physics in Perspective |volume=4|issue=4|pages=399–420|doi=10.1007/s000160200002|bibcode=2002PhP.....4..399S|s2cid=121785335}}</ref> Raman took Duane's side and said, "Compton, you're a very good debater, but the truth isn't in you."<ref name="Banerjee-2014" />