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IEVref:112-02-10ID:
Language:enStatus: Standard
Term: candela
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Symbol: cd
Definition: SI unit of luminous intensity, equal to the luminous intensity in a given direction, of a source that emits monochromatic radiation of frequency 540נ1012Hz and has a radiant intensity in that direction of 1/683W/sr

Note 1 to entry: The definition in the SI Brochure is:"The candela, symbol cd, is the SI unit of luminous intensity in a given direction. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540נ1012Hz, Kcd, to be 683 when expressed in the unit lmW−1, which is equal to cdsrW−1, or cdsrkg−1m−2s3, where the kilogram, metre and second are defined in terms of h, c and ΔνCs."

Note 2 to entry: This definition implies that 683lm/W is the exact value of the luminous efficacy of monochromatic radiation Km.

Note 3 to entry: The candela is one of the seven SI base units: second (s), metre (m), kilogram (kg), ampere (A), kelvin (K), mole (mol) and candela (cd).


Publication date:2020-12
Source:SI Brochure, 9th edition, 2019, 2.3.1, modified – The definition in the SI Brochure has been revised to comply with the IEV rules. Notes 1 to 3 to entry have been added.
Replaces:112-02-10:2010-01
Internal notes:2020-12-10: Correction to Note 1 to entry: "minus" deleted in "monochromatic radiation of frequency 540 10−12 Hz". The French is already correct. JGO
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