How Do You Calculate Luminous Flux for Different Wavelengths?

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The luminous flux for a radiant flux of 3 watts at a wavelength of 6000 Angstrom is calculated to be 1403.565 lumens using the formula: Total luminous flux = (radiant flux) x (Relative luminosity) x (Peak value of luminous efficacy in a photopic vision curve). The relative luminosity for 6000 Angstrom is 0.685, and the peak luminous efficacy is 683 lumen/watt. An alternative calculation suggests using 667 lumen/watt based on the conversion of one lumen to 1.5 x 10^(-3) watts for monochromatic light at 5550 Angstrom.

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Amith2006
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Please help me with this problem.
# 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, Peak value of luminous efficacy in a photopic vision curve = 683 lumen/watt
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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Since you are given
Amith2006 said:
One lumen is equivalent to 1.5 x 10^(-3) watts of monochromatic light of wavelength 5550 Angstrom
perhaps you are meant to use 1/(1.5 x 10^(-3)) =667 lumen/W, not 683.
 

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