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Homework Help: Energy level problem

  1. May 28, 2006 #1
    A hydrogen atom, initially at rest in the n = 4 quantum state, undergoes a transition to the ground state, emitting a photon in the process. What is the speed (in terms of m/s) of the recoiling hydrogen atom?

    anyone knows what to do? i calculated the energy difference and got 12.75 eV and i calculated the potential energy as well, but i don't know which mass to assign the atom...

    any help is appreciated...
     
  2. jcsd
  3. May 28, 2006 #2

    Doc Al

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    Staff: Mentor

    (1) What's conserved during the emission?
    (2) You can look up the mass of a hydrogen atom!
     
  4. May 28, 2006 #3
    reply

    well, that's the thing- the problem doesn't state anything more than I put on there... the mass of a hydrogen atom will be that of 1 proton, but i'm not sure if that's what i should look for...

    any thoughts?
     
  5. May 29, 2006 #4

    Doc Al

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    Staff: Mentor

    You don't need any more information to solve the problem. What's the answer to my first question? (Hint: In any kind of "explosion", what's conserved?)
     
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