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Question about spectral lines

  1. May 12, 2009 #1
    i'm a newbie to quantum theory so bear with me please :) when hydrogen is heated in a vaccuum, the electron gets excited and moves to a higher energy level right? and then emits light as a spectral line when it moves back down to the lower energy level. my question is, why does it only show up as a line? shouldn't it be a continual spectrum of light between the two energy levels? the energy we see as light is the electron's movement isn't it? (or is that something else?) sorry for all the questions, and thanks if you can help!
  2. jcsd
  3. May 12, 2009 #2


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    Yea, that's what happens when you try to think of QM in a classical mindset. In quantum mechanics, a transition down a level for an electron emits exactly 1 photon with the energy of the transition. Because all the electrons make more or less the same transitions, you get a stream of photons with the same energy and therefore frequency. So, you get a line and not a continuum.
  4. May 12, 2009 #3
    An electron is thought to behave as a wave, and waves can add or subtract (destructive interference). In most places the electron is tuned out by destructive interference. And in few places the electron can exist where its wavelike nature adds up to itself (constructive interference). That's why its energy level is discreet.

    This youtube video demonstrates interference. Resonant patterns occur at certain frequencies > energy levels.

    Last edited by a moderator: Sep 25, 2014
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