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Quantum - potential difference problem.

  1. Jan 14, 2006 #1

    A certain proton needs to have a lamba of 0.0055 x 10^-9m. What potential difference must this proton be accelerated to achieve this wavelength?

    what i know:

    im assuming that what we need to find in this question is the amount of kinetic enegry needed to achieve such a lambda.

    E = hv / y y will represent lambda
    i also know that
    Ek = eV <--- potential difference
    and that
    Ek = 1/2mv^2

    so eV = 1/2mv^2
    and v is = E x lambda / h


    eV = 1/2m (eV x lamba / h) ^2

    am i on the right track here or am i completly lost??
  2. jcsd
  3. Jan 14, 2006 #2


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    Staff Emeritus
    Science Advisor

    It depends on whether or not the proton is relativistic.

    You are looking for the potential which will impart a kinetic energy to a proton such the wavelength is as given.

    See - http://hyperphysics.phy-astr.gsu.edu/hbase/debrog.html#c3

    You might try the relativistic and non-relativistic formulae to see the difference.
  4. Jan 15, 2006 #3
    hmmm, will do.

    thanks for the help
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