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# A screen receives 3 watts of radiant flux of wavelength 6000 Angstrom. One lumen is equivalent to 1.5 x 10^(-3) watts of monochromatic light of wavelength 5550 Angstrom. If the relative luminosity for 6000 Angstrom is 0.685 while that for 5550 Angstrom is 1, then what is the luminous flux of the source?

I solved it in the following way:

Here radiant flux = 3 watts, Relative luminosity at 6000 Angstrom = 0.685

Total luminous flux = (radiant flux) x (Relative luminosity) x (Peak value of luminous efficacy in a photopic vision curve)

= 3 x 0.685 x 683

= 1403.565 lumens

Is it right?

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# Homework Help: Photopic efficacy problem

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