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Lumen (unit)

(Redirected from Lm)

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.

Lamp efficiency
Lamp type Lumens per watt
Incandescent light bulb 11-16
Compact fluorescent 50-70
Metal halide lamp 80-120
Sodium vapor lamp 90-150

SI light units

Last updated: 07-29-2005 21:36:28
Last updated: 08-19-2005 04:35:36