Visible Spectrum
History
History
Newton's color circle, from Opticks of 1704, showing the colors correlated with musical notes. The spectral colors from red to violet are divided by the notes of the musical scale, starting at D. The circle completes a full octave, from D to D. Newton's circle places red, at one end of the spectrum, next to violet, at the other. This reflects the fact that non-spectral purple colors are observed when red and violet light are mixed.
Two of the earliest explanations of the optical spectrum came from Isaac Newton, when he wrote his Opticks, and from Goethe, in his Theory of Colours, although earlier observations had been made by Roger Bacon who first recognized the visible spectrum in a glass of water, four centuries before Newton discovered that prisms could disassemble and reassemble white light.
Newton first used the word spectrum (Latin for "appearance" or "apparition") in print in 1671 in describing his experiments in optics. The word "spectrum" [Spektrum] was strictly used to designate a ghostly optical afterimage by Goethe in his Theory of Colors and Schopenhauer in On Vision and Colors. Newton observed that when a narrow beam of sunlight strikes the face of a glass prism at an angle, some is reflected and some of the beam passes into and through the glass, emerging as different colored bands. Newton hypothesized that light was made up of "corpuscles" (particles) of different colors, and that the different colors of light moved at different speeds in transparent matter, with red light moving more quickly in glass than violet. The result is that red light bends (refracted) less sharply than violet as it passes through the prism, creating a spectrum of colors.
Newton divided the spectrum into seven named colors: red, orange, yellow, green, blue, indigo, and violet. (Some schoolchildren memorize this order using the mnemonic ROY G. BIV.) He chose seven colors out of a belief, derived from the ancient Greek sophists, that there was a connection between the colors, the musical notes, the known objects in the solar system, and the days of the week. The human eye is relatively insensitive to indigo's frequencies, and some otherwise well-sighted people cannot distinguish indigo from blue and violet. For this reason some commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right but merely as a shade of blue or violet.
Johann Wolfgang von Goethe argued that the continuous spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum, but rather reddish-yellow and blue-cyan edges with white between them. The spectrum only appears when these edges are close enough to overlap.
In the early 19th century, the concept of the visible spectrum became more definite, as light outside the visible rangeltraviolet and infraredas discovered and characterized by William Herschel, Johann Wilhelm Ritter, Thomas Young, Thomas Johann Seebeck, and others. Young was the first to measure the wavelengths of different colors of light, in 1802.
The connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century. Their theory of color vision correctly proposed that the eye uses three distinct receptors to perceive color.
Spectral colors
Color
Wavelength
Frequency
violet
380450nm
668789THz
blue
450495nm
606668THz
green
495570nm
526606THz
yellow
570590nm
508526THz
orange
590620nm
484508THz
red
620750nm
400484THz
Colors that can be produced by visible light of a single wavelength (monochromatic light) are referred to as the pure spectral colors.
Although the spectrum is continuous, with no clear boundaries between one color and the next, the ranges may be used as an approximation.
Spectroscopy
Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light.
Spectroscopy is the study of objects based on the spectrum of color they emit or absorb. Spectroscopy is an important investigative tool in astronomy where scientists use it to analyze the properties of distant objects. Typically, astronomical spectroscopy uses high-dispersion diffraction gratings to observe spectra at very high spectral resolutions. Helium was first detected by analyzing the spectrum of the Sun. Chemical elements can be detected in astronomical objects by emission lines and absorption lines. The shifting of spectral lines can be used to measure the red shift or blue shift of distant or fast-moving objects. The first exoplanets were discovered by analyzing the Doppler shift of stars at a resolution that revealed variations in radial velocity as small as a few meters per second. The presence of planets was revealed by their gravitational influence on the motion of the stars.
Color display spectrum
Color spectrum generated in a display device.
Color displays (e.g., computer monitors and televisions) mix red, green, and blue color to create colors within their respective color triangles, and so can only approximately represent spectral colors, which are in general outside any color triangle.
A render of the color spectrum into the sRGB color space on a gray background.
A render of the color spectrum into the sRGB color space on a brown background.
Colors outside the color gamut of the display device result in negative values. If color accurate reproduction of the spectrum is desired, negative values can be avoided by rendering the spectra on a gray background. This gives an accurate simulation of looking at a spectrum on a gray background.
Scanning
The world of desktop scanners has crossed the threshold of Deep Color where scanners are capable of capturing a billion or more colors.
See also
Wikisource has original text related to this article:
Definition of the Color Indigo
Color vision
High-energy visible light
Deep Color
References
^ Cecie Starr (2005). Biology: Concepts and Applications. Thomson Brooks/Cole. ISBN 053446226X. http://books.google.com/books?id=RtSpGV_Pl_0C&pg=PA94.
^ Cuthill, Innes C; et al. (1997). "Ultraviolet vision in birds". in Peter J.B. Slater. Advances in the Study of Behavior. 29. Oxford, England: Academic Press. p.161. ISBN 978-0-12-004529-7.
^ Jamieson, Barrie G. M. (2007). Reproductive Biology and Phylogeny of Birds. Charlottesville VA: University of Virginia. p.128. ISBN 1578083869.
^ Coffey, Peter (1912). The Science of Logic: An Inquiry Into the Principles of Accurate Thought. Longmans. http://books.google.com/books?id=j8BCAAAAIAAJ&pg=PA185&dq;="roger+bacon"+prism&ei=TX8OSJ2jMZCSzQTKx8y7Ag&client=firefox-a.
^ Hutchison, Niels (2004). "Music For Measure: On the 300th Anniversary of Newton's Opticks". Colour Music. http://home.vicnet.net.au/~colmusic/opticks3.htm. Retrieved 2006-08-11.
^ Newton, Isaac (1704). Opticks.
^ Mary Jo Nye (editor) (2003). The Cambridge History of Science: The Modern Physical and Mathematical Sciences. 5. Cambridge University Press. p.278. ISBN 9780521571999. http://books.google.com/books?id=B3WvWhJTTX8C&pg=PA278&dq=spectrum+"thomas+young"+herschel+ritter&lr;=&as_brr=0&as_pt=ALLTYPES&ei=XZT2Se_dF4vOkwT9tMigBA.
^ John C. D. Brand (1995). Lines of light: the sources of dispersive spectroscopy, 1800-1930. CRC Press. p.3032. ISBN 9782884491631. http://books.google.com/books?id=sKx0IBC22p4C&pg=PA30&dq=light+wavelength+color++young+fresnel&as_brr=3&ei=zpX2SdWLIpDmkASaxq3LBA#PPA31,M1.
^ Thomas J. Bruno, Paris D. N. Svoronos. CRC Handbook of Fundamental Spectroscopic Correlation Charts. CRC Press, 2005.
^ http://www.repairfaq.org/sam/repspec/
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Electromagnetic spectrum
shorter wavelengthslonger wavelengths
Gamma rays X-rays Ultraviolet Visible Infrared Terahertz radiation Microwave Radio
Visible (optical)
Violet Blue Green Yellow Orange Red
Microwaves
W band V band Q band Ka band K band Ku band X band S band C band L band
Radio
EHF SHF UHF VHF HF MF LF VLF ULF SLF ELF
Wavelength types
Microwave Shortwave Medium wave Longwave
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Color vision
Color vision Color blindness Opponent process
Monochromacy Dichromacy Trichromacy Tetrachromacy Pentachromacy
See Color space for mathematical representation models.
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Radiation (Physics & Health)
Main articles
Non-ionizing radiation
Ultraviolet light Near ultraviolet Visible light Infrared light Microwave Radio waves Acoustic Radiation
Ionizing radiation
X-ray Cosmic radiation Gamma ray Background radiation Nuclear fission Nuclear fusion Particle accelerators Nuclear radiation (nuclear weapons Nuclear reactors) Radioactive materials (Radioactive decay)
Thermal radiation Electromagnetic radiation Earth's radiation balance
Radiation health effects
Radiation therapy Radiation poisoning Skin effect Radioactivity in biological research List of civilian radiation accidents
Mobile phone radiation and health Wireless electronic devices and health Health physics Laser safety Lasers and aviation safety
Related articles
Radiation hardening Half-life Radiobiology Nuclear physics
See also: Category:Radiation effects Category:Radioactivity Category:Radiation health effects Category:Radiobiology
Categories: Color | Electromagnetic spectrum | Optical spectrum | Vision
Visible Spectrum
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