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Homework Help: Clarification needed in tunneling problem

  1. Oct 14, 2008 #1
    1. The problem statement, all variables and given/known data

    In a particular semiconductor device, electrons that are accelerated through a potential of 5 V attempt to tunnel through a barrier of width 0.8 nm and height 10 V. What fraction of the electrons are able to tunnel through the barrier if the potential is zero outside the barrier?

    2. Relevant equations

    k= (2m(V-E)/h)^1/2


    3. The attempt at a solution

    This is an example problem in my text book that is very similar to a homework problem. When solving for k, the value the book inserts for "m" is "0.511 x 10^6 eV / c^2"

    I deduced this is a substitution for m by rearranging E=mc^2 . What I do not understand is what this "E" value of 0.511 x 10^6 represents. When I devide that by the speed of light squared it does not equal the mass of an electron (9.10938188 × 10-31 kilograms) like i think it should, isntead it equals 5.677 x 10^-12
  2. jcsd
  3. Oct 15, 2008 #2


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    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi joker314! Welcome to PF! :smile:

    You need to revise your electric units … eV and kg are different units. :wink:

    A volt is a joule per coulomb, so an eV is a J times the charge of an electron (I think :rolleyes:).
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