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Homework Help: Modern Physics, Finding wave length problem! wee

  1. Apr 12, 2006 #1
    Modern Physics, Finding wave length problem! wee!!

    Ello ello!
    I'm having troubles getting this table started. The directions are:
    Use the Bohr diagram shown below to complete the following table.

    Tell the wavelength and color of light emitted when the following energy level changes occur.
    Orbital change
    n = 4 to n = 1
    Wavelength = ?


    Well once i find the wave length i'm pretty sure i can just look at the table, and find the correct color it corresponds too.

    So if n = 4, that looks like its pointing to the UV spectrum, but what are those numbers under it? such as: 397 389 etc

    So it goes to n =1, that means it is going to give off light. and n =1 looks lkike its still in the UV spectrum. so would i take the wave lengths:
    397 - 389 = 8nm? i'm assuming those numbers are in nano meters. So the color type would be UV which i got right. But i'm still confused on the wave length. I subbmited 8nm as my answer and it was wrong.Any help would be great! :biggrin:
  2. jcsd
  3. Apr 12, 2006 #2


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    Gold Member

    In the circular diagram, there is an arrow that signals the n=4 to n=1 transition. The arrow signifies the photon that is emitted when an electron drops from the n=4 to n=1 state.

    Yes the numbers are the wavelength in nanometers.
  4. Apr 12, 2006 #3

    Doc Al

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    Staff: Mentor

    Just follow the arrows; they point to the wavelength of the photon emitted for each transition.

    Each line in the spectrum has its wavelength listed.

    No need to subtract anything. Find the n = 4 to 1 transition, follow the arrow, then read off the wavelength.
  5. Apr 12, 2006 #4
    thanks guys that worked for the first, the answer was: 389 nm, and it was UV. I just looked at n4 and followed the arrow to the 389.
    but i went onto the next one which is:
    n = 4 n = 2, i wrote down the wave length of the n = 2, and the n =4, both wrong and its also saying its not even UV light anymore. But if u follow the arrows n = 2, and n = 4 are both in the UV. Any ideas what i'm misinterpreting? thanks!
  6. Apr 12, 2006 #5

    Doc Al

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    Staff: Mentor

    A wavelength corresponds to a transition between two levels, so to say that you found the wavelength for n = 2 or n = 4 doesn't make sense. Find the arrow that shows the electron falling from n = 4 to n = 2; that's the one you want.
  7. Apr 12, 2006 #6
    Oo i got what your saying now! thanks a ton Doc!
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