Koshel, R. John Photon Engineering, LLC, Tucson, Arizona.
Last reviewed:January 2020
- Related Primary Literature
- Additional Reading
The photometric intensity of visible radiation in the electromagnetic spectrum after taking into consideration the response of the human visual system to the radiant intensity. The International Commission on Illumination (abbreviated CIE, due to its French form: Commission Internationale de l'Éclairage) maintains standards for the sensitivity of the human eye to visible light as a function of wavelength and viewing conditions. The term, light, typically is used for the visible spectrum, but it is often extended into the infrared and ultraviolet regions. The standard visible spectrum is based on the photopic curve, which has been refined since its establishment by the CIE in 1924. The visible spectrum is defined to extend over a range of wavelengths from 380 to 780 nm. Luminous intensity typically is represented by the symbol Iν, where the subscript ν denotes a photometric quantity, and its unit is the candela, an SI base unit (1 cd = 1 lumen/steradian, where the steradian is a measure of solid angle). An antiquated term for the candela is candlepower. Luminous intensity is equal to the differential luminous flux (Φν, with units of lumen) per differential solid angle (Ω, a dimensionless quantity expressed in steradians), as in Eq. (1).
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 10,000 highly qualified scientists and 45 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information