Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    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

    User Avatar

    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

    User Avatar

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