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Homework Help: Expectation value of x

  1. Aug 2, 2007 #1
    I am trying to find <x> for

    [tex] \psi(x,t) = A exp\left(-|x|/L - i*E*t/\hbar\right)[/tex]

    I found the normalization factor of 1/L and I took

    [tex] \int_{-\infty}^{\infty}\left( x * exp(|x|/L) \right) [/tex] in two

    integrals however I got as a final result:

    [tex] L * -\infty * exp(-\infty/ L) - L * \infty * exp( - \infty /L) [/tex]

    Is that 0?
  2. jcsd
  3. Aug 2, 2007 #2
    I believe your answer tends towards zero:

    [tex]L * -\infty * exp(-\infty/ L) - L * \infty * exp( - \infty /L) = -2 * L * \infty * exp(-\infty/ L) -> -\infty/exp(\infty) -> 0[/tex]
  4. Aug 2, 2007 #3
    I see. That's the problem with throwing around infinities instead of using limits.
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