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Homework Help: Spectral lines from multiple atoms

  1. Nov 7, 2013 #1
    1. The problem statement, all variables and given/known data

    "A gas discharge tube contains H 1 , H2, He 3 , He4, Li6, and Li7 ions and atoms (the superscript
    is the atomic mass), with the last four ionized so as to have only one electron. (a)
    As the potential across the tube is raised from zero, which spectral line should appear
    first? (b) Give, in order of increasing frequency, the origin of the lines corresponding to the
    first line of the Lyman series of H 1 ."

    2. Relevant equations

    3. The attempt at a solution

    I have no problem with part (a), but I don't quite get what they're asking for in part (b).
  2. jcsd
  3. Nov 7, 2013 #2
    The first line of the Lymann series originates from a transition from the second to the first energy level of hydrogen.
    I guess that they want the lines form the other ions and atoms of similar transitions in the order of increasing frequencies. So you need state them in increasing frequencies order and specify from which ion or atom they originate.
  4. Nov 7, 2013 #3
    That's basically what I was thinking, but the phrase "the origin of" was throwing me off. Without that phrase, that part is also pretty straight-forward, since I would just use the reduced mass Rydberg equation to calculate the frequency of the spectral line in each atom with n: 2->1. But with the phrase, it sounds like they want me to find the frequency for the first Lyman transition for the hydrogen, helium, and lithium without taking the reduced mass effect into account.
  5. Nov 7, 2013 #4


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    Staff: Mentor

    I think "origin" just means the isotope.
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