Re: Luminance to candlepower and inverse square law

As long as the diameter of the beam increases linearly with distance
from the source, the beam area will increase as the square of the
distance, and the intensity ( = power/area ) will vary as the
inverse-square.

This condition is generally satisfied for lamp sources for distances
greater than several times the actual source size. Laser beams follow
the inverse-square law at large enough distances too (in the
"far-field")

Mark

Misterbeets wrote:
> Hi,
>
> I'm calculating candlepower of a lamp based on a luminance
measurement
> of its diffuse reflection, using a correction factor based on the
> square of the separation between the lamp and the reflector.
>
> My question is, I thought this particular inverse square law only
> applied to a point source radiating into a sphere, not a directional
> lamp like an auto tail light. Am I wrong?
>
> Thanks,
>
> JB

.

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