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Homework Help: QM- Why is the separation constant +/-l(l+1) ?

  1. Oct 24, 2011 #1
    This isn't a HW problem, it's more of a general question. I'm reading Griffith's Intro to QM 3rd Edition. On page 134 he uses separation of variables, of which I'm familiar (but by no means an expert). Could someone explain why the separation constant in equations 4.16 and 4.17 changes sign?

    The equations in question : http://imgur.com/8OKqz" [Broken]
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Oct 24, 2011 #2


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    If you look at the equation above those two, you see the terms sum to 0, so if one is positive, the other one is negative.
  4. Oct 24, 2011 #3
    Jeez, that should have been obvious!
    Thanks for your help.
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