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Photon + H2 collision

  1. Jul 15, 2007 #1
    So if a H2 molecule collides with and absorbs a photon of wavelength around 60nm, I find the final velocity of H2 molecule (assuming momentum's conserved in collision) to be around 3.5 m/s, which I think is very small... I would have thought that since the wavelength of the photon is so small, the energy of it is pretty high, which means H2 should move much faster than just 3.5 m/s after the collision... it just doesn't make sense to me conceptually, I guess. Is there something wrong with my logic?
  2. jcsd
  3. Jul 15, 2007 #2

    Meir Achuz

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    Only in questioning your answer, which is correct.
    The velocity is slow because H2 is so massive.
    Preconception is the mother of confusion.
  4. Jul 15, 2007 #3


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    Hi. Just curious. What text did this question come out of? Are there any further questions about the internal excitation energy of the H2 molecule after the collision?
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