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Quantum Mechanical Tunneling Probability

  1. Sep 21, 2012 #1
    I recently took an exam in which the professor asked the following question:

    Suppose an object of mass 2 grams were incident on a rectangular barrier of height 20 cm and width 2.0 cm. What is the probability that the object will quantum mechanically tunnel and appear on the other side?

    I argued that since this object has a mass on the order of 10^27 times greater than the electron that qualitatively the probability would be negligible. Furthermore I argued that such a macroscopic object could be described classically so why would we describe such an object by a wave-function propagating in space? I'd like to hear your ideas on the matter and see what others say. Thanks!
  2. jcsd
  3. Sep 21, 2012 #2


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    I'd say that you're right, it's "negligible", but your professor probably wanted you to come up with a number. You have to play to the audience. :smile:

    I'd also say that Schrodinger quantum mechanics is intended to describe a point particle, and treating a 2 gram object as if it were a point particle is pretty hokey. What if half the object penetrated the barrier and the other half did not?
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