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Homework Help: Calculation of Luminous flux

  1. Jun 26, 2006 #1
    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?
  2. jcsd
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