Light Intensity: Is it Decreasing at 1/r2?

[hiltac]

Hello,
If we consider a source of light (in a point x), is it wright to say that the intensity decreases in 1/r² ?

Thank you !

 

[mfb]

If r is the distance to point x, it is right. Note that there are no exactly point-like sources of light, so for real sources this is only an approximation.

 

[DaveC426913]

Does this apply to any light? Including, say, a laser?

 

[mfb]

Very far away from the source, yes, as you are always limited by diffraction. For a laser pointer (or all visible light lasers with a similar beam diameter), it becomes a good approximation after several hundred meters.

This assumes no absorption or other elements (like lenses) in the path, of course.