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Homework Help: Lyman Series

  1. Aug 2, 2007 #1
    1. The problem statement, all variables and given/known data
    A hydrogen atom at rest in the laboratory emits the Lyman radiation.
    (a) Compute the recoil kinetic energy of the atom.
    (b) What fraction of the excitation energy of the n = 2 state is carried by the recoiling atom? (Hint: Use conservation of momentum.)

    2. Relevant equations

    3. The attempt at a solution
    I'm not sure if this equation is relevant, but I'm not sure what they are referring to when they say recoil kinetic energy of the atom.
  2. jcsd
  3. Aug 2, 2007 #2


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    (Hint: Use conservation of momentum.) The departing photon carries momentum. The atom must have an equal and opposite momentum (hence a nonzero kinetic energy). The total energy of the two is the Lyman transition energy.
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