The relative luminosity of wavelength 600 nm is0.6 Find the radiant flux of 600 nm needed to produce the same brightness sensation as produced by 120 W of radiant flux at 555nm.

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Solution

Relative luminousity

Luminous flux of a source of

$= \frac{g i v e n w a v e l e n g t h}{L u m i n o u s f l u x o f a s o u r c e o f}$

555 nm of same power

$∴$ Let the radiant flux needed by P watt

So,

$0.6 = \frac{L u m i n o u s f l u x o f a s o u r c e P w a t t}{684 P}$ $\Rightarrow$

Luminous flux of the source, (685 P)

$\times 0.6 = 120 \times 685$

$\Rightarrow$ $P = \frac{120}{0.6} = 200 W$

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Similar questions

A source emits light of wavelengths 555 nm and 600 nm. The radiant flux of the 555 nm part is 40 W and of the 600 nm part is 30 W.The relative luminosity at 600 nm is 0.6 . Find (a) the total radiant flux, (b) the total luminous flux, (c) the luminous efficiency.

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The relative luminosity of wavelength 600 nm is0.6 Find the radiant flux of 600 nm needed to produce the same brightness sensation as produced by 120 W of radiant flux at 555nm.

Relative luminousity Luminous flux of a source of =given wavelengthLuminous flux of a source of 555 nm of same power ∴ Let the radiant flux needed by P watt So, 0.6=Luminous flux of a source P watt684 P ⇒ Luminous flux of the source, (685 P) × 0.6=120×685 ⇒ P=1200.6=200 W