Question

A screen receives 3 watt of radiant flux of wave length 6000 angstorm. 685 lumen are equivalent to 1 watt of monochromatic light of wavelength 5550 angstrom. If relative to that for 5550 angstorm, then what is the luminous flux of the source?

Answer 1

To calculate the luminous flux of the source, we need to convert the radiant flux (in watts) to luminous flux (in lumens) using the luminous efficacy.

Luminous efficacy is a measure of how efficiently a light source produces visible light relative to other wavelengths. In this case, we are given that 685 lumens are equivalent to 1 watt of monochromatic light with a wavelength of 5550 angstroms.

Let's calculate the luminous flux using the given information:

1. Convert the radiant flux to watts: Radiant flux = 3 watts

2. Determine the luminous efficacy: Luminous efficacy = 685 lumens / 1 watt (5550 angstroms)

3. Calculate the luminous flux: Luminous flux = Radiant flux × Luminous efficacy

   Luminous flux = 3 watts × (685 lumens / 1 watt) = 2055 lumens

Therefore, the luminous flux of the source is 2055 lumens.