candela(redirected from unit of light)
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candela(kăndĕ`lə), in weights and measures: see candlecandle,
in weights and measures, unit of luminous intensity; it is defined as 1-60 of the intensity of a blackbody, or ideal radiator, at the temperature at which platinum solidifies (2,046°K;).
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the unit of luminous intensity, formerly called candle. The candela is one of the seven base units of the International System of Units. Its definition was made more precise by the 13th General Conference on Weights and Measures in 1967. The candela is defined in terms of the primary photometric standard—a blackbody radiator at the temperature of solidification of platinum. The symbol for the unit is cd. The candela, or new candle, superseded in 1948 the international candle, which had been established in 1909. The international candle came into use in 1921 and was used in the USSR from 1925.
The same means of reproducing the unit of luminous intensity have been used in the USSR as abroad—incandescent lamps or a group standard. A verbal definition of the unit was given in OST (All-Union Standard) 4891 in 1935 and in the Statute on Photometric Units in 1948. This definition was based on the lumen in accordance with the structure of the system of photometric quantities: an international candle is the luminous intensity of a point source of light in the directions where the source emits a luminous flux of 1 lumen uniformly distributed within a solid angle of 1 steradian. In GOST (All-Union State Standard) 7932–56, Photometric Units, for the sake of uniformity with other countries the candela was defined as the basic photometric unit. An international candle is equal to 1.005 candelas.
V. E. KARTASHEVSKAIA