We are creating the world's most trusted encyclopedia and knowledge base. Once you join us and log in, you'll be able to edit this page instantly!

From Citizendium, the Citizens' Compendium

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.

References

1. ↑ International Bureau of Weights and Measures