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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.

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.

Grade:11

1 Answers

Jitender Pal
askIITians Faculty 365 Points
8 years ago
Sol. Relative luminousity = Lu min ous flux of a source of given wavelength/ Lu min ous flux of a source of 555 nm of same power Let the radiant flux needed be P watt. Ao, 0.6 = Lu min ous flux of source ‘P’ watt/685 P ∴ Luminous flux of the source = (685 P)× 0.6 = 120 × 685 ⇒ P = 120/0.6 = 200 W

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