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Homework Help: Neon signs

  1. Mar 23, 2006 #1
    need to hand in an assingment in an hour.
    would appreciate help on this :

    "Does the light emitted by a neon sign constitute a continuous spectrum or only a few colors? Defend your answer"

    thank you
  2. jcsd
  3. Mar 23, 2006 #2


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    Gold Member

    And what is you take on the subject? Defend yourself.

    P.S. This belongs in the homework section.
  4. Mar 23, 2006 #3
    oops sorry !

    well i've replied that the light constitute only a few colours because neon emits strongly in the red - orange region
    mercury in ultra violet and so on. each element corresponds to different wavelengths.

    though i'm not sure. i guess mainly because i'm not too sure what the question is asking me.
  5. Mar 23, 2006 #4


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    Staff Emeritus
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    Gold Member

    I think your answer is correct. The fact the neon lights have a very specific colour, as do sodium lights etc. kinda gives it away.

  6. Mar 23, 2006 #5
    oh good thanks :)

    another verification if you don't mind
    the question asks if the Bohr model contredicts in any way classical physics.
    i replied that only the first assumption that the electrons are fixed in circular orbits violates the laws of classical mechanics - of the idea of centripetal acceleration (???)
    am i right to say that?
    did i miss anything else? :-S
  7. Mar 23, 2006 #6
    What's wrong with circular orbits?

    (That was a rhetorical question...)

    The answer is in classical electrodynamics and radiation. Another possible answer involves a violation of special relativity.
  8. Mar 23, 2006 #7


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    Staff: Mentor

    Yeah, what would happen if the electron were just spinning around in a classical orbit around the nucleus? Would there be a natural loss of energy for some reason?
  9. Mar 23, 2006 #8
    Accelerating charges radiate an EM field. So if an electron were in orbit around, say, a proton it would slowly spiral inward as the electon's kinetic energy is lost to the outgoing EM field.

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