SI coherent derived unit whose name and symbol includes an SI coherent derived unit with a special name and symbol
|Name||Symbol||Derived quantity||Expressed in terms of SI base units|
|lumen second||lm s||luminous energy||s cd|
The lumen second, symbol lm s, is the SI coherent derived unit of luminous energy, a measure of the total quantity of visible light emitted by a source.
Luminous energy is a measure of the total quantity of visible light emitted by a source.
The lumen second is analogous to the watt second, or joule.
Luminous energy differs from radiant energy, in that radiant energy includes electromagnetic waves at all emitted frequencies, while luminous energy is weighted according to the human eye’s sensitivity to different frequencies, or wavelengths.
|Name||Symbol||Quantity||Expressed in terms of SI base units||Expressed in terms of other SI units|
|lumen||lm||luminous flux||cd||cd sr|
|candela per square metre||m-2 cd||luminance||m-2 cd||cd/m2|
|lumen second||lm s||luminous energy||s cd||lm s|
|lumen per watt||lm W‑1||luminous efficacy||kg‑1 m‑2 s3 cd||lm/W|