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Emitted Photons

  1. Sep 21, 2008 #1
    1. The problem statement, all variables and given/known data
    A hydrogen atom has its electron in the n = 2 state. The electron makes a transition to the ground state. The linear momentum of the emitted photon is E/c. If we assume conservation of linear momentum, what is the recoil velocity of the atom?

    2. Relevant equations

    [tex]v_n = \frac {e^2}{2 \epsilon_0 h n}[/tex]

    3. The attempt at a solution

    Momentum Before:
    [tex]p_i = m_e v_e[/tex]
    where [tex]v_e = \frac{e^2}{4 \epsilon_0 h }[/tex]

    Momentum After:
    [tex]p_f = E/c + m_? v_{recoil}[/tex]

    My question is: Is this analysis correct? and
    For Bohr atoms do what mass do I use (mass of a proton and a neutron, or just a proton?)

    I am questioning the way I set this up because I don't know what the nucleus contains (proton and neutron or just a proton).
  2. jcsd
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