Lamp efficiency is measured in

• A. Lux/watt
• B. Candela/watt
• C. Lumen/watt
• D. Lumen/lux

Answer: (C)

The luminous efficiency of an electric lamp is the ratio of the luminous flux (in lumen) emitted by the lamp to the electric power (watt) given to it i.e.
Luminous efficiency η = Luminous flux/Watt
Note:-  Lumens is the unit of measurement for luminous flux, which is the total amount of visible light emitted by a source.
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