Q8 of 38 Page 455

A source emits 314 W of a radiant flux distributed uniformly in all directions. The luminous efficiency is 60 lumen . What is the luminous intensity of the source?

Given that,
Radiant flux = 31.4 W
Since the radiant flux is distributed uniformly in all directions, the solid angle will be Luminous efficiency = 60 lumen/W


So, luminous flux = luminous efficiency × radiant flux
= 60 × 31.4 lumen





So, the luminous intensity of the source is 150 Cd.


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

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