A) 50W
B) 72W
C) \[120\times {{(0.6)}^{2}}W\]
D) 200W
Correct Answer: D
Solution :
If h is the luminous efficiency of the bulb then. luminous flux by 120 watt at 555 nm \[=\eta \times 120\] Let bulb of P watt at 600 nm produces the same luminous flux as by 120 watt at 555 nm then \[\eta \times 120=\eta P\times 0.6\] \[\Rightarrow P=\frac{120}{0.6}=200\ watt.\]
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