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Laser pointer and CD

  1. Feb 8, 2014 #1
    When I point my red laser pointer at the playable side of a CD at an angle the spot becomes diffracted, a bit like the fringes you can get if you put a hair across the beam.

    Could you keep to the CD phenomenon, when trying to explain and whether it really is related to Youngs Fringes or Heisenberg's Uncertainty principle please.
    Thank you
  2. jcsd
  3. Feb 8, 2014 #2


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    This doesn't need Heisenberg (there are smartarse ways of doing it - as usual - but it's not the best way to approach any of this stuff at this sort of level). Treat it as straight Diffraction. The Max's and Min's are there because of the way the reflections from each part of the disc add up (vectorially) in the various directions. Treat these things in terms of waves and you can't go wrong. Waves are just as valid as particles and you should get competent enough with the wave approach before launching into particles. Probability densities, and all that, are great when you really know what you are doing but some approaches to problem solving are harder than making love standing up in a hammock.
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