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Step up and Step down Potentials

  1. Apr 28, 2012 #1
    1. The problem statement, all variables and given/known data

    What fraction of a beam of 8 eV electrons is reflected by a potential step up of height 6 eV? What fraction is reflected from a step down of 6eV?


    2. Relevant equations

    R=[itex](\frac{k_{1}-k_{2}}{k_{1}+k_{2}})^{2}[/itex]

    Exchange [itex]k_{1}[/itex] and [itex]k_{2}[/itex] for the step down potential.

    [itex]k_{1}[/itex]=[itex]\frac{\sqrt{2mE}}{h/2pi}[/itex]

    [itex]k_{2}[/itex]=[itex]\frac{\sqrt{2m(E-U0)}}{h/2pi}[/itex]

    3. The attempt at a solution

    I got 1/9 for the step up.

    But I got the same for the step down potential, which I don't think is right. Am I doing anything wrong for the step down potential? Or should you get the same answer for the step down as for the step up?
     
    Last edited: Apr 28, 2012
  2. jcsd
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