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Light as waves

  1. Nov 14, 2015 #1
    scientists have observed light acting as waves on a macroscopic scale before the quantum characteristics of particles were discovered. My question is what sets apart the macroscopic wavelike characteristcs of light apart from other matter waves? This may be a stupid question but can the macroscopic observation of light waves just be an emergence of the probability waves of photons?
     
  2. jcsd
  3. Nov 14, 2015 #2

    BvU

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    Not a stupid question. In a sense: yes. (to the second question: if there's no probability to observe a photon, you son't see it). A bit corny, I concede.
    So if you can steer me in another direction, please do.

    For the first question, I would say: the fact that the wavelength is in the visible range.

    I don't think you should consider light as matter waves: photons have no mass.
     
  4. Nov 14, 2015 #3

    bhobba

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    The idea of matter waves was consigned to the dustbin of history when Dirac came up with his transformation theory at the end of 1926 (probably sooner - but certainly by then):
    http://www.lajpe.org/may08/09_Carlos_Madrid.pdf

    Thanks
    Bill
     
  5. Nov 15, 2015 #4

    BvU

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    Thanks Bill, but it seems to me that is heavy ammunition for Chris. The original question hints at a sense of wonder over the actual difference between light waves and matter waves. And I find it hard to pinpoint that without resorting to indicating rest mass as the only difference: to me that's more a microscopic difference. It doesn't help to say that you can have a kilogram of protons at rest and not a kilogram of photons.

    Wave characteristics of matter behaviour popped up long after light was understood in terms of wave behaviour, and it came as a surprise that the core physical differences are virtually none. Conversely, light demonstrates particle behaviour (as in the photoelectric effect) making it even more complicated for a while.

    Chris' question is at the very heart of of physics. Not current physics any more, but physics at a very peak in its development over time !
     
  6. Nov 15, 2015 #5
    so just to be clear, macroscopic light interference patterns, such as the airy disk or young's double slit, are just the photons quantum probability waves in action?
     
  7. Nov 15, 2015 #6

    ZapperZ

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    Just so you know, we don't have to switch to using the classical wave picture to account for the interference (and other wave-like behavior) of light. We can definitely describe such a feature using quantum mechanical description. The Marcella paper that I've referenced to many times is one such example of this treatment.

    So no, this wave-like behavior isn't just a "macroscopic" observation, because it can be described microscopically and all the way up.

    Zz.
     
  8. Nov 15, 2015 #7

    bhobba

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    At the beginner level that's the way its usually viewed.

    However it isn't true because position is not an observable for photons. Explaining that at the beginner level though isn't easy:
    http://www.mat.univie.ac.at/~neum/physfaq/topics/position.html

    Unfortunately sometimes in physics its like that - what is taught at the beginner level needs to be unlearned later. Its a royal pain in the toosh for beginners that come here because we don't 'sugar' coat it.

    Thanks
    Bill
     
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