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Source of light

  1. Jan 28, 2015 #1
    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 !
     
  2. jcsd
  3. Jan 28, 2015 #2

    mfb

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    Staff: Mentor

    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.
     
  4. Jan 28, 2015 #3

    DaveC426913

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    Does this apply to any light? Including, say, a laser?
     
  5. Jan 28, 2015 #4

    mfb

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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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