In physics, specifically photometry (optics), the lumen (symbol: lm) is the SI derived unit of luminous flux. It is the amount of light that falls on a unit area at unit distance from a source of one candela. A 100 watt incandescent light bulb will output around 1400 lumens.
Efficiency
The efficiency of a lamp can be expressed in lumens per watt. In general, a higher-powered lamp will be more efficient, so that a 100W bulb will produce more lumination per unit of power than a 60W bulb of the same type.
SI light units
Last updated: 06-02-2005 13:08:33
