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Homework Help: Quantum expectation values

  1. Oct 12, 2009 #1
    1. The problem statement, all variables and given/known data

    Consider a particle in an infinite one-dimensional box that has a length L and is centered at the origin. (Use h for Planck's constant, n, and L, as necessary.) Evaluate <x^2> for <x^2> at n=1.

    2. Relevant equations

    <x^2>= (2/L)[(L^3/24)-(L^3/4n^2*pi^2)cos(n*pi)]

    3. The attempt at a solution

    I used this formula and got the answer (L^2/12)+(L^2/(2*pi^2)). My assignment is telling me this is incorrect. I took the same approach for the second part of my homework asking for this when n=2, and I got (L^2/12)-(L^2/(8*pi^2)) which it says is correct. I cannot figure out why my first answer is not correct as well. Any help would be much appreciated.
  2. jcsd
  3. Oct 13, 2009 #2
    Sorry. Just figured it out.
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