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Homework Help: Normalization of a Wave Function

  1. May 29, 2009 #1


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    1. The problem statement, all variables and given/known data
    I'm starting to (trying) teach myself some quantum mechanics out of the Griffiths book, and since there are no answers in the back I have no idea if I'm on the right track or not. Could you guys look over the answer to this equation to see if it looks right?

    Consider the wave function [tex] \Psi(x,t) = A e^{-\lambda |x|}e^{-i \omega t}[/tex]

    a Normalize [tex]\Psi[/tex]

    2. Relevant equations
    [tex] 1 = \int^\infty_{-\infty} | \Psi |^2 dx [/tex]

    3. The attempt at a solution
    [tex]|\Psi(x,t)|^2 = (\Psi*)\Psi[/tex]
    [tex]\Psi* = A e^{-\lambda |x|}e^{i \omega t}[/tex]
    [tex]|\Psi(x,t)|^2 = A^2e^{-2 \lambda |x|}[/tex]

    [tex] 1 = \int^\infty_{-\infty} A^2e^{-2 \lambda |x|} dx = \frac{A^2}{\lambda} [/tex]
    [tex] A = \sqrt{\lambda}[/tex]

    Look correct?
  2. jcsd
  3. May 29, 2009 #2


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    Homework Helper

    That is correct. Don't forget you can check your answer by integrating the function with your normalization constant plugged in.
  4. May 29, 2009 #3
    Here, the absolute value becomes a problem. The absolute value makes the integrand an even function. That means that the final function is symetric about the y axis. What you can do is drop the absolute value, Integrate from 0 to infinity, and multiply the result by two.
  5. May 29, 2009 #4
    Oh wait, you did the integral already. Well, that's what you would do if you were actually doing the math rather than using a table or computer program.
  6. May 30, 2009 #5


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    i did the integral mathematically exactly the way you said! I wasn't completely sure that this was the correct way to evaluate the absolute value, but I had a feeling it was. I'm a math major in addition to being a physics major =)
  7. May 30, 2009 #6
    This lies within the tips and tricks that are learned slowly and never taught explicitly. When they are taught explicitly, they are often not understood at the time.
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