Question

A 1000w bulb filled with a reflector illuminates an area of 3m*3m with an average illumination of 450 lux. If the bulb has an efficiency of 9 lumens/watt the efficiency of the reflector is

Answer 1

Answer: The efficiency of the reflector is 45%

Explanation:

Given that,  

Lumens = 1000 W

Area = 3m X 3m

Flux = 450 lux

Efficiency = 9 lumens/watt

We know that,

Total lumens $= E\times \dfrac{A}{\eta}$

The efficiency of the reflector is

$9\ l/w\times 1000\ w= 450\ lux\times\dfrac{9\ m^{2}}{\eta}\times 100$

$\eta = 45\%$

Hence, the efficiency of the reflector is 45%