Question

A source emits 31.4 W of radiant flux distributed uniformly in all directions. The luminous efficiency is 60 lumen watt⁻¹. What is the luminous intensity of the source?

Answer 1

Given that,

Radiant flux = 31.4 W

Since the radiant flux is distributed uniformly in all directions, the solid angle will be 4π Luminous efficiency = 60 lumen/W

So, luminous flux = luminous efficiency × radiant flux

= 60 × 31.4 lumen

Luminous intensity = `"Luminous flux"/"Solid angle"="Luminous flux"/(4pi)`

`=(60xx(31.4))/(4pi)`

= 150 candela