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Rontgen's discovery of x-rays - question

  1. Jul 10, 2009 #1
    When Rontgen discovered x-rays in 1895, was he witnessing K-shell emission or Brehmsstrahlung radiation?
  2. jcsd
  3. Jul 10, 2009 #2


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    Staff: Mentor

    I don't have a definite answer, but I think I know what you need to look for.

    From Yale: An Historical Overview of the Discovery of the X-Ray

    From this, it appears that in Röntgen's Lenard tube, the X-rays were produced by cathode rays (electrons) impinging on an aluminum sheet ("window") in the wall of the tube.

    If the electron energy is above the K-shell ionization energy for aluminum, then it can kick out a K-shell electron, and you can have K-shell emission.

    So you need to find out the K-shell energy for aluminum, and the voltage on Röntgen's Lenard tube (which gives you the energy of the electrons in eV).

    Below the K-shell energy, it can be only bremsstrahlung. Above that energy, both processes can take place.

    By a strange coincidence, last week, while traveling through Germany, I stood outside the building in Würzburg where Röntgen made his discovery. Unfortunately, the museum inside was closed that day. :frown:

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  4. Jul 10, 2009 #3
    If you look at a typical X ray spectrum you will see that it consists of the discrete K,L etc lines superimposed upon a smoothly varying bremmstrahlung background and that most of the energy emitted is in the form of bremmstrahlung.I think Rontgen called them X rays because he didn't know what they were and so he used X, the symbol for the unknown.
  5. Jul 10, 2009 #4


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    Staff: Mentor

    Right, in general you have both effects. But if the cathode-ray energy was low enough, then Röntgen would have seen only bremsstrahlung.
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