Light Intensity: Is it Decreasing at 1/r2?

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SUMMARY

The intensity of light from a point source decreases according to the inverse square law, specifically at a rate of 1/r², where r represents the distance from the source. This principle holds true for real-world light sources, including lasers, although it is an approximation due to the non-point-like nature of actual light sources. For lasers, this approximation becomes accurate at distances of several hundred meters, provided there are no intervening factors such as absorption or lenses affecting the light path.

PREREQUISITES
  • Understanding of the inverse square law in physics
  • Basic knowledge of light propagation and diffraction
  • Familiarity with laser technology and its characteristics
  • Concept of light absorption and its effects on intensity
NEXT STEPS
  • Research the inverse square law in greater detail
  • Explore the principles of light diffraction and its impact on laser beams
  • Study the effects of absorption on light intensity in different mediums
  • Investigate practical applications of lasers over long distances
USEFUL FOR

Physicists, optical engineers, and anyone interested in the behavior of light and its applications in technology, particularly in fields involving lasers and light intensity measurement.

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