Question

A light source emits monochromatic light of  555 nwavelengthm. The source consumes 100 W of electric power and emits 35 W of radiant flux. Calculate the overall luminous efficiency.

Answer 1

Given:
Wavelength of light, λ = 555 nm

Radiant flux emitted = 35 W

Power input = 100 W

Overall luminous efficiency = `"Total luminous flux"/"Power input"=(35xx685)/100=239.75 "lm/W"`

So, the overall luminous efficiency will be 240 lm/W.