Editing Blue (section)

==Optics and colour theory==

The term ''blue'' generally describes colours perceived by humans observing light with a [[dominant wavelength]] between approximately 450 and 495&nbsp;nanometres.<ref>{{Cite web |title=Wavelength of Blue and Red Light |url=https://scied.ucar.edu/image/wavelength-blue-and-red-light-image |access-date=25 June 2022 |website=Center for Science Education}}</ref> Blues with a higher frequency and thus a shorter wavelength gradually look more violet, while those with a lower frequency and a longer wavelength gradually appear more green. Purer blues are in the middle of this range, e.g., around 470&nbsp;nanometres.

[[Isaac Newton]] included blue as one of the seven colours in his first description of the [[visible spectrum]].<ref>{{Cite web |date=2015 |title=The Science of Color |url=https://library.si.edu/exhibition/color-in-a-new-light/science |access-date=25 June 2022 |website=library.si.edu}}</ref> He chose seven colours because that was the number of notes in the musical scale, which he believed was related to the optical spectrum. He included [[indigo]], the hue between blue and violet, as one of the separate colours, though today it is usually considered a hue of blue.<ref>Arthur C. Hardy and Fred H. Perrin. ''The Principles of Optics.'' McGraw-Hill Book Co., Inc., New York. 1932.</ref>

In painting and traditional [[colour theory]], blue is one of the three [[primary color|primary colours]] of pigments (red, yellow, blue), which can be mixed to form a wide [[gamut]] of colours. Red and blue mixed together form violet, blue and yellow together form green. Mixing all three primary colours together produces a dark brown. From the Renaissance onward, painters used this system to create their colours (see [[RYB colour model]]).

The RYB model was used for [[colour printing]] by [[Jacob Christoph Le Blon]] as early as 1725. Later, printers discovered that more accurate colours could be created by using combinations of cyan, magenta, yellow, and black ink, put onto separate inked plates and then overlaid one at a time onto paper. This method could produce almost all the colours in the [[spectrum]] with reasonable accuracy.

<gallery mode="packed" heights="150px">
File:AdditiveColorMixing.svg|Additive colour mixing. The combination of [[primary colour]]s produces secondary colours where two overlap; the combination red, green, and blue each in full intensity makes white.
File:Closeup of pixels.JPG|Red, green, and blue [[subpixels]] on a [[liquid-crystal display]].
</gallery>

On the [[HSL and HSV|HSV colour wheel]], the [[Complementary color|complement]] of blue is [[yellow]]; that is, a colour corresponding to an equal mixture of [[red]] and [[green]] light. On a colour wheel based on traditional colour theory ([[RYB colour model|RYB]]) where blue was considered a primary colour, its complementary colour is considered to be [[orange (colour)|orange]] (based on the [[Munsell color system|Munsell colour wheel]]).<ref>{{Cite web |last=Sandra Espinet |title=Glossary Term: Color wheel |url=http://www.sanford-artedventures.com/study/g_color_wheel.html |access-date=25 June 2022 |website=Sanford-artedventures.com |archive-date=7 September 2008 |archive-url=https://web.archive.org/web/20080907184837/http://www.sanford-artedventures.com/study/g_color_wheel.html |url-status=dead }}</ref>

===LED===
{{main|Blue LED}}

In 1993, high-brightness blue LEDs were demonstrated by [[Shuji Nakamura]] of [[Nichia Corporation]].<ref name="Nakamura">{{cite journal | title=Candela-Class High-Brightness InGaN/AlGaN Double-Heterostructure Blue-Light-Emitting-Diodes | last1=Nakamura | first1=S. | last2=Mukai | first2=T. | last3=Senoh | first3=M. | journal=[[Applied Physics Letters]] | year=1994 | volume=64 | page=1687 | bibcode=1994ApPhL..64.1687N | doi=10.1063/1.111832 | issue=13  |issn=0003-6951}}</ref><ref>{{cite web |last1=Nakamura |first1=Shuji |title=Development of the Blue Light-Emitting Diode |url=http://spie.org/x115688.xml |publisher=SPIE Newsroom |access-date=28 September 2015}}</ref><ref>Iwasa, Naruhito; Mukai, Takashi and Nakamura, Shuji {{US patent|5578839}} "Light-emitting gallium nitride-based compound semiconductor device" Issue date: 26 November 1996</ref> In parallel, [[Isamu Akasaki]] and [[Hiroshi Amano]] of [[Nagoya University]] were working on a new development which revolutionized LED lighting.<ref>{{cite web |date=12 January 2023 |title=Professor Shuji Nakamura was key to the Invention of Blu-Ray Technology |url=https://ssleec.ucsb.edu/news/2023/01/12/professor-shuji-nakamura-was-key-invention-blu-ray-technology |archive-url=https://web.archive.org/web/20230324123538/https://ssleec.ucsb.edu/news/2023/01/12/professor-shuji-nakamura-was-key-invention-blu-ray-technology |archive-date=24 March 2023 |access-date=4 June 2023 |publisher=[[University of California, Santa Barbara]]}}</ref><ref>{{cite web|url=https://www.nae.edu/128641/Dr-Shuji-Nakamura-|archive-url=https://web.archive.org/web/20190411125926/https://www.nae.edu/128641/Dr-Shuji-Nakamura-|title= Dr. Shuji Nakamura|publisher=[[National Academy of Engineering]]|archive-date=11 April 2019|access-date=4 June 2023}}</ref>

Nakamura was awarded the 2006 [[Millennium Technology Prize]] for his invention.<ref>[https://www.news.ucsb.edu/2006/012148/2006-millennium-technology-prize 2006 Millennium technology prize awarded to UCSB's Shuji Nakamura]. Ia.ucsb.edu (15 June 2006). Retrieved on 3 August 2019.</ref>
Nakamura, [[Hiroshi Amano]] and [[Isamu Akasaki]] were awarded the [[Nobel Prize in Physics]] in 2014 for the invention of an efficient blue LED.<ref name="NYT-20141007-DO">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Nobel Prize in Physics |url=https://www.nytimes.com/2014/10/08/science/isamu-akasaki-hiroshi-amano-and-shuji-nakamura-awarded-the-nobel-prize-in-physics.html |date=7 October 2014 |work=[[The New York Times]] }}</ref>

===Lasers===
{{main|Blue laser}}

[[Laser]]s emitting in the blue region of the spectrum became widely available to the public in 2010 with the release of inexpensive high-powered 445–447&nbsp;nm [[laser diode]] technology.<ref name="laserglow">{{Cite web |title=Laserglow – Blue, Red, Yellow, Green Lasers |url=http://www.laserglow.com/GPO |url-status=live |archive-url=https://web.archive.org/web/20110916051206/http://www.laserglow.com/GPO |archive-date=16 September 2011 |access-date=20 September 2011 |website=Laserglow.com}}</ref> Previously the blue wavelengths were accessible only through [[DPSS]] which are comparatively expensive and inefficient, but still widely used by scientists for applications including [[optogenetics]], [[Raman spectroscopy]], and [[particle image velocimetry]], due to their superior beam quality.<ref name="laserglow2">{{Cite web |title=Laserglow – Optogenetics |url=http://www.laserglow.com/page/optogenetics |url-status=live |archive-url=https://web.archive.org/web/20110915023159/http://www.laserglow.com/page/optogenetics |archive-date=15 September 2011 |access-date=20 September 2011 |website=Laserglow.com}}</ref> Blue [[gas laser]]s are also still commonly used for [[holography]], [[DNA sequencing]], [[optical pumping]], among other scientific and medical applications.