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Characteristic Scale Arguments

  1. Oct 26, 2014 #1
    In physics one often invokes arguments about a characteristic scale. For example at distances much larger than the Compton wavelength (a characteristic length scale) one might ignore quantum phenomena and calculate classically.

    I would like to read up some more on the thinking behind such arguments, their validity etc. Does anyone know of some good literature on this topic?
  2. jcsd
  3. Oct 26, 2014 #2


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    First of all, my mother language is not English, so I'll be glad if you correct any mistake.

    The Compton wavelength is a particular case of the "de Broglie length wave" for electrons. The great idea behind this concept is the complementarity principle.


    The complementarity in quantum physics could be summarized as "propagating as a wave; interacting with matter as a particle".

    When you detect a quanta, you will measure its properties as a particle. When you don't detect a quanta, but its interference with itself, you will measure its properties as a wave, and among other things, its "de Broglie's wavelength".

    It's a tricky point, and I think the best introduction is a historical view. I would recommend you The Nobel Lecture of de Broglie. http://www.nobelprize.org/nobel_prizes/physics/laureates/1929/broglie-lecture.pdf. The textbook Eisberg&Resnick, Quantum Physics, which is often used for the first year of quantum physics classes at university, has a nice historical introduction.

    And an even deeper text is "The Feynman Lectures on Physics". Vol. 3-4, p. 221-222, 412.

    PD: Quantum phenomena are not only related to small sizes; a very graphical example is when you try to measure the temperature of a water droplet with a mercury-in-glass thermometer: this is also quantum physics :)
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