A 500 W bulb fitted with a reflector illuminates an area of 2 m x 2 m with an average illumination of 500 lux.

A 500 W bulb fitted with a reflector illuminates an area of 2 m x 2 m with an average illumination of 500 lux. The efficiency of the reflector is 50%. The efficiency of the bulb in lumens/watt is : 
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A 500 W bulb fitted with a reflector illuminates an area of 2 m x 2 m with an average illumination of 500 lux. The efficiency of the reflector is 50%. The efficiency of the bulb in lumens/watt is : 8

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