An incandescent bulb produces 520 lumens and has an efficacy of 13 lm over cap w What is the power of the bulb?
Answer
A
40 cap w
B
503 cap w
C
2 point 5 cap w
D
533 cap w
Explanation
Efficacy is the light output in lumens divided by power in watts. Rearranging gives power = 520 lm ÷ 13 lm/W = 40 W. Therefore, the correct choice is 40 W.
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