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Homework Help: Questions in QM!

  1. Dec 13, 2006 #1
    Q1
    energy no. of times measured
    a1 n1
    a2 n2
    a3 n3
    a4 n4

    expectation value <E> = (a1n1+a2n2+a3n3+a4n4) / (n1+n2+n3+n4)
    is this correct?

    Also, how do you caluculate expectation value <E^2> ?
    i.e. <E squared>

    Q2
    Identify if the following functions are eigenfunctions of the parity operator.

    a) f(z) = z(a-z)(z+b), where a,b are real numbers
    b) f(x) = Ψ(x)xΨ(x), where Ψ(x) is antisymmetric about the origin.
    c) same f(x) in b), but where Ψ(x) is symmetric about the origin.
    d) f(x) = Ψ(x)x^2Ψ(x) where Ψ(x) is antisymmetric about the origin. x^2 means x squared.
     
  2. jcsd
  3. Dec 13, 2006 #2

    dextercioby

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    How did you come up with the first answer ? Follow the same line of thought and you'll find the answer to <E^2>.

    Post ideas and work, people here want to help, not supply full solutions to your problems.

    Daniel.
     
  4. Dec 13, 2006 #3
    so i said <E> = (a1n1+a2n2+a3n3+a4n4) / (n1+n2+n3+n4)

    and if this was correct,

    <E^2> = (a1^2 n1 + a2^2 n2 + a3^2 n3 + a4^2 n4) / (n1+n2+n3+n4)

    is this correct??

    Q2, my thought was:
    only d was eigenfunctions of the parity operator.

    b,c always give function to the power of odd value, a i just worked out can not be...
     
  5. Dec 13, 2006 #4

    OlderDan

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    Both of these look good.
     
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