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

Wave function -- Why is there an imaginary part?

  1. Dec 1, 2015 #1
    If wave is a real concept, then why we have a complex(imaginary) part associated with the wave function?
     
  2. jcsd
  3. Dec 1, 2015 #2

    Krylov

    User Avatar
    Science Advisor
    Education Advisor

    It is the squared modulus of the wave function (= a probability distribution) that is of physical interest, since it predicts the likelihood that physical observables assume certain values. The wave function itself cannot be measured and, as far as I know, does not have a physical meaning.
     
  4. Dec 1, 2015 #3
    Ordinary waves are modeled as complex numbers too though. It's not a quantum-only thing. https://en.wikipedia.org/wiki/Phasor
     
  5. Dec 1, 2015 #4

    PeroK

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    An imaginary number is not imaginary. That's just a word someone dreamt up one day! Complex numbers are just as "real" as vectors, matrices and continuous functions.
     
  6. Dec 1, 2015 #5

    bhobba

    User Avatar
    Science Advisor
    Gold Member

    Technically its got to do with the requirement for continuous transformations between quantum states. If a system is in a state and one second later is in another state then we reasonably expect that after half a second it went through some state in getting there. It turns out if you require that then so called imaginary numbers are required:
    http://www.scottaaronson.com/democritus/lec9.html

    BTW they are no more or less imaginary than say negative numbers. You cant point to a negative number of ducks for example. But if you owe someone two ducks then saying you have -2 ducks is very convenient. Same with imaginary numbers. You cant point to square root -1 (doubly so since you cant even point to -1 of anything) but in modelling some things its very convenient to introduce it - QM being a good example.

    Thanks
    Bill
     
    Last edited: Dec 2, 2015
  7. Dec 3, 2015 #6
    Classical mechanics can also be described in terms of complex wave functions, so they aren't inherently quantum mechanical things.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Wave function -- Why is there an imaginary part?
Loading...