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Bremsstrahlung Radiation

  1. Mar 22, 2015 #1
    Hi, I am having some difficulty understanding some of the concepts in involved in Bremsstrahlung Radiation. I have recently been learning about the Rutherford scattering experiment where an alpha particle is fired towards a gold nucleus. In my book there is a fairly simple derivation of how you can estimate the size of the nucleus from an alpha particle that goes head on towards a gold nucleus and gets back scattered. It says that since an alpha particle is positive then it will slow down as it heads towards the gold nucleus. It will then come to a complete stop and then get repelled back the way it came in. My book uses conservation of energy where it sets the kinetic energy of the alpha particle equal to the electrostatic potential energy at closest approach (since at this point all of the KE will be converted in electric PE). If you then solve for 'r' you get a number that is very close to the actual size of a nucleus. These concepts (as far as I can see) seem to clash with what I have read up about Bremsstrahlung Radiation. This radiation seems to be caused when electrons fired at a target atom get repelled and change direction due to interactions with the electric field of other electrons and/or the nucleus. Since this causes accelerations of the electrons that have been fired, electromagnetic radiation (namely X-rays) can be given off. If you apply the science behind Rutherford's scattering experiment then these electrons should come in with very high kinetic energies. They then lose KE but this gets converted into electrical PE. Surely this is conservation of energy so how is there room for electromagnetic radiation to be given off as well? Surely if the description of Bremsstrahlung Radiation is correct then the value of the size of the atom given by Rutherford's scattering experiment would be way off since you can't assume all the KE to be converted to electrical PE as some will be radiated as EM radiation as the alpha particle accelerates/decelerates?
  2. jcsd
  3. Mar 22, 2015 #2


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    Staff: Mentor

    Electrons and alpha particles are not the same. The bremsstrahlung process depends on the mass of the particle, and this differs by a factor of roughly 8000 for the two different types.
    Yes there might be some energy loss for the alpha particles due to radiation, but it is negligible.
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