Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Psi Wave Function Constant

  1. Jun 12, 2014 #1
    What is the "A" in the wave equation: [itex]Ae^{i(kx-wt)}[/itex]? What does it mean in quantum mechanics? Is it just the amplitude?
     
  2. jcsd
  3. Jun 12, 2014 #2

    Matterwave

    User Avatar
    Science Advisor
    Gold Member

    In quantum mechanics, it would normally be a normalization constant. Except, if that wave equation were taken to be over all space, it is not normalizable.

    So under some circumstances, you can think of it like an amplitude, for problems involving, e.g. scattering. But only ratios should ever be used if we are using plane wave approximations.
     
  4. Jun 12, 2014 #3

    bhobba

    User Avatar
    Science Advisor
    Gold Member

    A is sometimes (but not always) set by where you got it from eg if you are considering a state of definite momentum that is modelled by Dirac Delta function it determines A in the position representation eg:
    http://hitoshi.berkeley.edu/221a/delta.pdf

    But sometimes thats not the case eg (see section 7.7 on the free particle):
    http://www.colorado.edu/physics/TZD/PageProofs1/TAYL07-203-247.I.pdf [Broken]

    However by looking at the momentum representation of the solution that would naturally set the value of the constant via the Dirac Delta function.

    It must always be remembered such states don't really exist, they are mathematical fictions introduced for convenience.

    Thanks
    Bill
     
    Last edited by a moderator: May 6, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook