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Homework Help: Heisenberg and wave-particle duality related questions

  1. Sep 22, 2008 #1
    Hello everyone. I've been reading the forums for a while so decided to register hoping to increase my learning curve in my physics and mathematics classes.

    I started back to college last year after a 5 year break since I had quit college. I was previously a music education major, so when I went back to school for physics I was WAY behind (and still am somewhat behind) mathematically.

    So in my modern physics class we're covering Heisenberg's Uncertainty Principle, wave-particle duality, and Schrodinger's equation. Uncertainty principle and wave particle duality I am starting to understand qualitatively. Still working on Schrodinger's equation (my mathematics deficiencies are hurting me on this one).

    In doing my homework, I came across a problem that reads:

    Supppose that a wave function describing the state of an electron predicted a statistical spread in the velocity of 10^-5m/s. What is the corresponding statistical spread in the position of the electron?

    I understand that i'm looking for a point, x, for which the electron will be located relative to the given velocity. But I'm not making the connection on what variables will get me to that point.

    I'm sure this is something basic that I'm overcomplicating, but hopefully someone is willing to point me in the right direction.

    The other question I could use some guidance on how to approach is: What size object woulld be necessary to observe neutron diffraction effects on a neutron with a kinetic energy of 10MeV? Is there anything in nature that would allow us to demonstrate the wave nature of a neutron with 10MeV kinetic energy?

    If i'm missing something blatantly obvious I apologize. Not asking anyone to solve the problems for me, just point me the right way.

    Thank you
  2. jcsd
  3. Sep 22, 2008 #2


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    Recall that velocity and momentum are related, and try getting your estimates with the Heisenberg uncertainty principle:
    http://zebu.uoregon.edu/~imamura/208/jan27/hup.html [Broken]

    Apparently quantum mechanics models particles as musical instruments! So it shouldn't be too difficult going from music to physics. Or at least that's what this guy claims: :smile:
    http://mitworld.mit.edu/video/253/ [Broken]

    Edit: According to Google, electron mass = 9.10938188 × 10-31 kilograms
    Last edited by a moderator: May 3, 2017
  4. Sep 22, 2008 #3
    thanks for the reply. It's funny how reading something worded just a little differently (the link you provide on HUP vs my text book) can make things more clear.

    a lot of the training in music in regards to playing in tune with other instruments or other musicians playing the same instrument can be seen in studying wave theory. Over the 15 years I was involved in music, there were indeed many occassions (almost constantly in the earlier years) where "beats" were created by two instruments playing the "same" tone but being out of tune between themselves. Was neat to see and analyze what causes that to happen in the class/lab.
  5. Sep 22, 2008 #4
    i jus have one question....wat does planks constant have to do with the uncertaint principle....
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