Optics Question 511
Question: The relative luminosity of wavelength 600 nm is 0.6. Find the radiant flux of 600 nm needed to produce the same brightness sensation as produced by 120 W of radiant flux at 555 nm
Options:
A) 50W
B) 72W
C) $ 120\times {{(0.6)}^{2}}W $
D) 200W
Show Answer
Answer:
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. $
