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I Wave-Particle Duality of Electrons

  1. May 31, 2017 #1
    The wave-particle duality of light was demonstrated first with Thomas Young's 1801 Interference Experiment...and then more clearly with the Double Slit Experiment. Both of these were done with light (so photons).

    My question is -- How did we come to understand the same of electrons? Did we manage to "pick an electron" off of an atom and attempt the experiment with it? When and how was the wave-particle duality of electrons demonstrated? As far as I've understood...electrons have a mass and a charge, wheres photons have no mass and no charge, so their properties are different.
     
  2. jcsd
  3. May 31, 2017 #2

    PeroK

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    You could start with this thread:

    https://www.physicsforums.com/threads/why-does-wave-particle-duality-not-exist-anymore.910647/
     
  4. May 31, 2017 #3
    Electrons were considered a wave because they also have a wavelength along with their mass, charge and spin.
    The theory part was proposed in order to support Neils Bohr's proposal that the energy of an electron is quantized by De Broglie.
    In truth they are now a kind of 'quantum' particle i.e. not exactly a particle nor a wave nor a field.
    You should check the link PeroK has provided.
     
  5. May 31, 2017 #4
    Thank you. I looked through it and it's useful. But I'm less concerned with what properties we understand an electron to have now, than I am with how we came to think that an electron has particle and wave properties and by what experimental set-up. Was it through no experimental set up? Was it via mathematics? I'm just trying to hone in on the period in scientific history when this idea that a photon has dual properties was also associated with the electron.
     
  6. May 31, 2017 #5

    Doc Al

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    You may want to look up the Davisson-Germer experiment, which was the classic experiment illustrating the "wave nature" of electrons; see these links:
    https://en.wikipedia.org/wiki/Davisson–Germer_experiment
    http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/DavGer2.html

    Since then, as you can imagine, many experiments have been done; in particular, check out the double slit experiment with electrons. See: https://en.wikipedia.org/wiki/Double-slit_experiment
     
  7. May 31, 2017 #6

    PeroK

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    I'm no expert on the history of QM but there must be plenty online about the history of the wave-particle duality.

    Perhaps someone else can add to this thread, but I suspect there are already several threads on here.

    PS I see @Doc Al has come to the rescue!
     
  8. May 31, 2017 #7
    Beautiful. Found it. "In 1924 Louis de Broglie presented his thesis concerning the wave–particle duality theory, which proposed the idea that all matter displays the wave–particle duality of photons." - Wikipedia. Thank you.
     
  9. May 31, 2017 #8

    PeterDonis

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    This demonstrated wave properties of light, but I'm not clear how it demonstrated wave-particle duality. At the time, I believe it was viewed as disproving the corpuscular theory of light that Newton, among others, had proposed, and validating the competing wave theory of light.
     
  10. May 31, 2017 #9

    Doc Al

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    I agree. The original double slit experiments were just seen as evidence of light being a wave.

    It was only much later that these experiments could be done one "particle" at a time (whether photon or electron or whatever), thus showing both wave and particle aspects.
     
  11. May 31, 2017 #10

    bhobba

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    If you want to read a good history of wave particle duality see:
    https://www.amazon.com/Einstein-Quantum-Quest-Valiant-Swabian/dp/1491531045

    But, while of critical importance, and its importance can not be overstated, to the development of QM, since the end of 1926 when Dirac came up with modern QM in his transformation theory, likely sooner, but certainly by then, it has been consigned to the dustbin of history replaced by QM proper which does not have the idea, except maybe in a very limited sense.

    Here is the history of that phase:
    http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.570.6345&rep=rep1&type=pdf

    Basically though the wave particle duality idea led to De-Broglie's ideas he wrote into a PhD thesis which Einstein recognized as a very important step in the right direction towards understanding the QM puzzle, but not the final answer. De-Broglie's professors didn't even understand it, but liked the math, and with Einsteins recommendation he got his Phd from the thesis and later a Nobel. Then someone asked Schrodinger a critical question - if electrons are sometimes waves they should obey a wave equation. He found one - the Schrodinger equation. But as my link above showed it then morphed into something else (modern QM) and he was sorry he ever became involved in it.

    Thanks
    Bill
     
    Last edited: Jun 2, 2017
  12. Jun 1, 2017 #11

    vanhees71

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    If it comes to the history of QT, there is the amazing multi-volume work by Mehra and Rechenberg on the subject. There you'll get everything in great detail. Nevertheless if you want to learn physics, too much history, particularly in learning QT, is more confusing than helpful. The confusion is natural since more than in other (classical) parts of physics, the problem of QT lies in the concepts (while the math is not as difficult as it looks; I found it easier to grasp than what's needed for classical electrodynamics), and these concepts had to be developed first, and there were a lot of misconceptions on the way to the now valid theory, among them (and indeed one of making the least sense of all) has been the idea of "wave-particle duality".
     
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