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Quantised Energy Levels - Bohr model

  1. Nov 2, 2005 #1
    Hi Guys,

    Because of the absorbtion and emmision spectrum we know that atoms have quantised engergy levels. For example for an electron to jump from ground state to the first excited state in a Mecury atom, a photon with the exact energy of 4.9eV is required.

    Now my question is what would happen if instead of a photon we fired an electron with 4.9eV of energy? Would the electron in the Mecury atom still jump to the first excited state? If so what happens to the incident electron?
  2. jcsd
  3. Nov 2, 2005 #2


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    Well, how do you think your fluorescent lights work? There's a thermionic cathode that emits electrons. These electrons are attracted to a positive anode, but in between, there's a gas (usually an inert gas). The electrons collide with the gas atoms, causing them to be excited and then decays with the emission of light. That's the light you see in neon lamps, etc.

    The electrons that did the colliding lost most of their energy, but get re-accelerated towards the anode, and the process gets repeated.

  4. Nov 2, 2005 #3
    Bohr postulates have been confirmed in Franck-Hertz experiment (see web) and that is exactly your case .

    (but I dont know what happens to incident electron with kinetic energy exactly 4,9eV but I guess repulsed)
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