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Knocking of electrons

  1. Sep 7, 2011 #1
    i studied that xrays can be produced when a vacancy created ,by knocking of electrons by other high velocity electrons, is filled by other electrons of outer shell. but can electron knock a electron? in same mass collision as in above just velocity is exchanged. so the orbiting electron will gain velocity of striking electron and escape. but as the velocity is just exchanged the striking electron will recieve orbital velocity and start orbiting the atom. so no vacancy is created. so how is this "vacancy thing" possible?
     
  2. jcsd
  3. Sep 8, 2011 #2

    alxm

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    That's a bit like saying that if I have a ball sitting on a post, and knock it off by throwing another ball on it,
    the second ball will always end up sitting on the post rather than them both flying off.

    The former can happen of course, but becomes increasingly unlikely as the ball you're throwing gets faster.
    That's essentially what's happening here (if we stay with the classical-analogy description).
     
  4. Sep 8, 2011 #3
    Hi.

    Electron knocking at another electron is dealt in Compton effect. I recommend to learn it.

    Regards.
     
  5. Sep 8, 2011 #4
    ABSOLUTELY NOT!!

    The Compton is strictly associated with a photon interacting with a "free" (i.e., loosely bound relative to the energy of the incident photon) electron and inelastic scattering off that electron.

    http://physics.about.com/od/quantumphysics/a/comptoneffect.htm" [Broken]
    http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/comptint.html" [Broken]
     
    Last edited by a moderator: May 5, 2017
  6. Sep 8, 2011 #5
    That's a bit like saying that if I have a ball sitting on a post, and knock it off by throwing another ball on it,
    the second ball will always end up sitting on the post rather than them both flying off.

    Even when the velocity becomes too high for two equal mass collision there is velocity exchage. this is as per law of conservation of linear momentum.
     
  7. Sep 8, 2011 #6

    alxm

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    Ok, let p1 and p2 be the momentum of the two particles before the collision, and p'1 and p'2 be the momenta after the collision. Conservation of momentum means: p1 + p2 = p'1 + p'2

    How do you get from that to p'2 = p1? Total momentum is conserved, not of the individual momenta of the particles.
     
  8. Sep 9, 2011 #7
    Hi.

    I was wrong. Electron-electron scattering is called Moller scattering.

    from Wiki
    Møller scattering is the name given to electron-electron scattering in Quantum Field Theory.

    Regards.
     
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