The relative luminosity of wavelength 600 nm is 06. 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.

Given,
Relative luminosity = 0.6
Let P be the radiant flux of the source.


∴ Luminous flux = P×685



Again,




⇒


⇒


So, 200 W radiant flux is needed to produce the same brightness sensation for 600 nm wavelength.


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