1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    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


    User Avatar
    Staff Emeritus
    Science Advisor
    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


    User Avatar

    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.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook