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Compton effect

  1. Sep 2, 2003 #1
    dear reader,
    what is comptons effect.how did compton do this experiment?[?] :smile:
  2. jcsd
  3. Sep 2, 2003 #2


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    Some background: It was in 1923 and he was studying the scattering of Xrays

    he would irradiate a sample of some material with Xrays of a known wavelength and measure the difference in wavelength of the Xrays scattered at some definite angle from the sample

    he found a formula which says that the bigger the angle of scattering the more of a reduction in energy of the Xrays----in other words the bigger the increase in wavelength

    [longer wavelength Xrays have less quantum energy and less penetrating power---he could measure the wavelength by measuring how thick a barrier the Xrays could penetrate]

    Compton assumed that the scattering was by outershell electrons in the material of the target. To a first approximation that is the Xray was scattered by one collision with one (essentially free floating) electron.the formula says

    increase in wavelength = (h/mc)(1 - cosine(scatter angle))

    = 0.0242 (1 - cosg) angstroms

    So if the angle of scatter was 90 degrees (with cosine zero) then the wavelength would be reduced by 0.02 angstroms

    This is headline news because it does not depend on the material and it does not depend on the incoming wavelength

    The original publication in 1923 was
    Physics Review volume 21 pages 207,483,715
    and volume 22, page 409

    I'm getting this out of a more-than-60 year old physics text that belonged to a physicist of the pre-1940 generation, it is a fascinating book and describes a lot of the early quantum physics experiments in considerable detail. Doubtless there is more to be had on the web.

    Compton's name was Arthur Holly Compton
    Last edited: Sep 2, 2003
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