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Rutherford Backscattering Experiment

  1. Aug 12, 2014 #1
    1. The problem statement, all variables and given/known data

    In the famous “Rutherford backscattering” experiment, alpha particles (Z=2) of
    approximately 7 MeV were used to bombard a Au (Z=79) film. Rutherford derived the
    scattering formula by treating an incident alpha particle and a Au target atom as two point
    charges with their charge numbers equal to their atomic numbers. This assumption, however,
    is not accurate in describing general ion solid interactions. Explain
    (a) why was Rutherford’s approach successful in his experiments?
    and
    (b) under what conditions deviation from Rutherford scattering formula will occur?



    2. Relevant equations



    3. The attempt at a solution

    a) Rutherford’s approach was successful because he used an extremely thin foil with a target nucleus much heavier than the incident alpha particles.

    b) If the foil was thicker and the target nucleus and incident alpha particle were of comparable mass, Rutherford would have observed increased ion-solid reaction types.
     
  2. jcsd
  3. Aug 12, 2014 #2

    mfb

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    2016 Award

    Staff: Mentor

    The thin foil is certainly an important point. The heavy nucleus is something the scattering formula can take into account.

    I think the question asks for something that you missed so far. What was the important historic result of the experiment? If you know the result in advance (as we do know) it might look obvious, but at that time it was unclear.
    Hint:
    What about electrons, for example?
     
  4. Aug 13, 2014 #3
    The result was confirmation of the atomic nucleus - most of the foil's mass is concentrated and not evenly distributed.
     
  5. Aug 13, 2014 #4

    mfb

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    2016 Award

    Staff: Mentor

    Right.
     
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