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Homework Help: Normalisation constant~ help

  1. Oct 15, 2008 #1
    Normalisation constant~ help~~

    1. The problem statement, all variables and given/known data

    An electron is in the spin state |> = A (3i, 4), so determine the normalisation constant A.

    2. Relevant equations

    :uhh: :frown:

    3. The attempt at a solution

    :cry: Well, I get confused about this questions, can anybody tell me what the normalisation constant is in this case? And does "in the spin state" mean something for given condition? Thanks a lot.
  2. jcsd
  3. Oct 15, 2008 #2


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    Re: Normalisation constant~ help~~

    Spin is simply a property that particles posses and this "spin state" describes, well the state of the spin of a particle or system of particles.

    As for the question, what does one normally mean when one says a "normalisation constant". What does it mean in the context of a wave function for example?
  4. Oct 15, 2008 #3
    Re: Normalisation constant~ help~~

    Well, thanks a lot, but i dont think this problem is discussing about wave function, I cannot find any concept about wave function in my lecture notes. Thus, I consider that this question is only about math and calculation. Or maybe you can teach me some about the wave function or any other ideas? Thanks any way~
  5. Oct 15, 2008 #4
    Re: Normalisation constant~ help~~

    Do you know about complex vectors? And how to normalize those to unit length?
  6. Oct 15, 2008 #5
    Re: Normalisation constant~ help~~

    yes, o! you mean I can just do it like A = 1/|(3i, 4)|?? Thanks!
  7. Oct 15, 2008 #6
    Re: Normalisation constant~ help~~

    Yep, that's all there is to it. But don't forget to simplify that expression for A you got now.
  8. Oct 16, 2008 #7
    Re: Normalisation constant~ help~~

    Thanks, so it's A = 1/5
  9. Oct 16, 2008 #8
    Re: Normalisation constant~ help~~

    So in Physics we can write the spin state as a function of the particle:

    [tex]|\psi \rangle = A \left ( \begin{array}{cc} 3i \\ 4 \end{array} \right)[/tex]

    But wave function must integrate to unity over all space, so:

    [tex]\langle \psi | \psi \rangle = 1 = A^2\left ( \begin{array}{cc} -3i & 4 \end{array} \right) \left ( \begin{array}{cc} 3i \\ 4 \end{array} \right) = 25A^2[/tex]

    So I agree with your answer
  10. Nov 1, 2009 #9
    Re: Normalisation constant~ help~~

    I friggin get it now!
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