Optics Question 476

Question: If luminous efficiency of a lamp is 2 lumen/watt and its luminous intensity is 42 candela, then power of the lamp is

[AFMC 1998]

Options:

A) 62 W

B) 76 W

C) 138 W

D) 264 W

Show Answer

Answer:

Correct Answer: D

Solution:

Luminous flux $ =4\pi \ L $

$ =4\times 3.14\times 42\ =\ 528 $

Lumen Power of lamp $ =\frac{Luminous\ flux}{Luminousefficiency} $

$ =\frac{528}{2}=264\ W $



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