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Judging distance of a light source

  1. Mar 21, 2009 #1
    Is there a way to judge the distance of a light source, or from where it was last reflected, by analyzing the characteristics of the light? Are there any properties of light that change, or better yet, consistently change over distance? I'm trying to figure out if somehow there would be a way to make a laser range finder type device, but by only analyzing the light received, and not having to emit anything.

    Thank you for your help.
  2. jcsd
  3. Mar 21, 2009 #2
    If you know something about the power of the light source, you may judge the distance, otherwise, it is impossible. Even though, the result may be affected a lot by the environment conditions : dust, humidity etc..
  4. Mar 22, 2009 #3
    Couldn't the angle of divergence tell you something amusing that it is a spherical source?
  5. Mar 22, 2009 #4
    When the light propagation in air or some other medium, the energy will be attenuating, due to the absorbs. So, you can judging the distance of the path length by measuring the energy loss.
    Usually, the light beam is not the perfect plane wave, the beam width also
    changes with the distance.
  6. Mar 22, 2009 #5


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    Gold Member

    What if you eimply triangluated the distance using parallax? Look at how a single-lens reflex camera can tell the distance to an object.
  7. Mar 22, 2009 #6
    Are you interested in a few miles or cosmic distances? If the latter, try ready about type 1a supernova (standard brilliance references) and analyzing cosmic microwave background radiation....over cosmic distances light is red shifted due to an expanding universe....
  8. Mar 22, 2009 #7
    I'm interested in short distances, from about 1-1000 meters. Thank you for your guidance so far, I'm looking into the way cameras tell distances when focusing like Dave pointed out.
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