Optics Question 489

Question: Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is

[CPMT 1992]

Options:

A) 80 W

B) 176 W

C) 88 W

D) 36 W

Show Answer

Answer:

Correct Answer: C

Solution:

Efficiency of light source η=φp ….. (i)

and L=φ4π ….. (ii) .

From equation (i) and (ii)

p=4πLη=4π×35588W .



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