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Homework Help: Minimum energy needed for a positrons to tunnel

  1. Mar 9, 2016 #1
    1. The problem statement, all variables and given/known data
    10^12 positrons of the same kinetic energy are incident on 10eV, 1nm barrier. What is the minimum kinetic energy the positrons need before any of them can penetrate the barrier?

    2. Relevant equations
    p_T = e^(-2*a*L)
    a = (sqrt(2m(V_0-E))/hbar

    3. The attempt at a solution

    For other problems I've plugged numbers into these equations to find non zero probabilities but this time I'm not sure how to solve it. I tried setting p_T to zero and rearranging for E but that just ended up as V_0=E.
  2. jcsd
  3. Mar 10, 2016 #2


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    Theoretically, they can pass the barrier regardless of their energy. It is just that the probability will be vanishingly small.

    What I would guess the problem wants you to do is to figure out when on average one positron will pass.

    Can you clarify the question?
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