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Homework Help: De Broglie Wavelength/Electron momentum

  1. Feb 13, 2016 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations
    Einsteins photon momentum: p=h/wavelength (rearrange to get de broglie wavelength)

    3. The attempt at a solution

    I am quite new to all this quantum physics stuff. First of all where is the momentum of the electron reffering to its angular momentum when it is orbiting? Can anyone explain this further to me. I think I need an equation here that relates the momentum to kinetic energy, I can't find anything like that.
  2. jcsd
  3. Feb 13, 2016 #2


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    Staff: Mentor

    No, this is linear momentum. You can simply imagine an electron traveling in a straight line.

    The relation is the same as in classical physics.
  4. Feb 13, 2016 #3
    Doesn't Einsteins relativity apply with electrons kinetic energy? I mean I don't think we can use KE=(1/2)mv^2
  5. Feb 13, 2016 #4
    Okay. I seem to have gotten somewhere further now. But my answer is incorrect, not too sure what to do with units. What is eV actually equal to in SI units?
  6. Feb 13, 2016 #5


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    Staff: Mentor

    What is the velocity corresponding to the momentum you calculated? Is it relativistic?

    First, you should write the units in the calculation you made, to make sure everything is correct.

    1 eV = 1.60218×10-19 (that wasn't hard to find with Google :wink:)

    By the way, you should commit to memory that ##E_K = p^2/(2m)##. It comes up all the time in quantum mechanics (and classical mechanics, for that matter).
  7. Feb 13, 2016 #6
    Alright. So I checked the units it and I am getting Joules for my kinetic energy which seems correct. My answer is wrong though not sure why?

    EDIT: I just realised its asking for answer in microeV, so ill just convert it. thanks for the help
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