Source of light

  • Thread starter hiltac
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  • #1
hiltac
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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 !
 

Answers and Replies

  • #2
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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.
 
  • #3
DaveC426913
Gold Member
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Does this apply to any light? Including, say, a laser?
 
  • #4
36,103
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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.
 

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