Candela: Difference between revisions
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The '''candela''' is the [[SI]] unit of [[luminous intensity]]. It is defined since 1979 as ''The luminous intensity, in a given direction, of a [light] source that emits monochromatic radiation of frequency 540 × 10<sup>12</sup> hertz and that has a radiant intensity in that direction of 1⁄683 watt per steradian.'' | The '''candela''' is the [[SI]] unit of [[luminous intensity]]. It is defined since 1979 as ''The luminous intensity, in a given direction, of a [light] source that emits monochromatic radiation of frequency 540 × 10<sup>12</sup> hertz and that has a radiant intensity in that direction of 1⁄683 watt per steradian.''<ref name=BIPM>[http://www.bipm.org/en/si/si_brochure/chapter2/2-1/candela.html International Bureau of Weights and Measures]</ref> | ||
An earlier definition, adopted in 1967, clarifying a definition adopted in 1946, was ''the luminous intensity, in the perpendicular direction, of a surface of 1⁄600,000th square meter of a [[Black-body radiation|blackbody]] at the temperature of freezing platinum under a pressure of 101,325 newtons per square meter [2042 K].'' | An earlier definition, adopted in 1967, clarifying a definition adopted in 1946, was ''the luminous intensity, in the perpendicular direction, of a surface of 1⁄600,000th square meter of a [[Black-body radiation|blackbody]] at the temperature of freezing platinum under a pressure of 101,325 newtons per square meter [2042 K].'' | ||
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==Sources== | ==Sources== | ||
*{{cite web|url=http://www.sizes.com/units/candela.htm|title=candela|publisher=Sizes.com|date=2007-03-08|accessdate=2007-05-11}} | *{{cite web|url=http://www.sizes.com/units/candela.htm|title=candela|publisher=Sizes.com|date=2007-03-08|accessdate=2007-05-11}} | ||
==References== | |||
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Revision as of 05:36, 17 February 2008
The candela is the SI unit of luminous intensity. It is defined since 1979 as The luminous intensity, in a given direction, of a [light] source that emits monochromatic radiation of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of 1⁄683 watt per steradian.[1]
An earlier definition, adopted in 1967, clarifying a definition adopted in 1946, was the luminous intensity, in the perpendicular direction, of a surface of 1⁄600,000th square meter of a blackbody at the temperature of freezing platinum under a pressure of 101,325 newtons per square meter [2042 K].
Sources
- candela. Sizes.com (2007-03-08). Retrieved on 2007-05-11.