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3 question of Ballmer experiment

  1. Oct 24, 2009 #1
    in Ballmer experiment we have a lamp of hydrogen gas and we put on it a high voltage in order to excite the electron . then we see 3 line of light. this 3 line of light are resulted from falling electron from layer with n=3 , 4 ,5 to layer with n=2.
    in Ballmer expriment which we see Ballmer series , at normal state the electron is in layer with n=1 and when we pun on high voltage on lamp of hydrogen for observing the Ballmer series the electron must go up to the layers above layer with n=2 and then come back to layer with n=2. why in this expriment the electron do not return to layer with n=1? because i think the electron at first was in layer with n=1 and after excitation it must return to ground state which is the layer with n=1.
    and if we use isotope of hydrogen instead of hydrogen whether the result of expriment change and why?
    and why we use hydrogen gas?
  2. jcsd
  3. Oct 24, 2009 #2
    Hi yashar-
    Very good questions. Of course, the electrons eventually have to return to the n=1 state. The transition wavelengths to the n=1 state (Lyman series) are shorter than the transitions to the n=2 state (Balmer series) and are in the ultra violet.
    Discharge lamps containing deuterium are available, and the Balmer series lines have slightly shorter wavelengths than hydrogen, due to the change in the reduced mass correction. This is easily measurable using a good diffraction grating.
    Bob S
  4. Oct 25, 2009 #3
    another question
    in Ballmer series does the electron fall from layer n=4 to layer n=3 .if does why we see 3 line of light that are originated from falling electron from layers n=3 , 4 , 5 to layer n=2 but we do not see the line of light that is originated from falling electron from layer n=4 to layer n=3 and there are just 3 line and no more line or why electron do not fall from (for example) layer n=9 to layer n=2.
    according to your previous answer i think taht the light that is originate from falling electron from layer n=9 to layer n=2 or from layer n=4 to layer n=3 is not in visible range of light. is this true?
    and do my english writing is understandable?
  5. Oct 25, 2009 #4


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    Staff: Mentor

    You have the formula for the hydrogen wavelengths, right? Calculate the wavelengths of the transitions in question and see for yourself whether they are in the visible range (about 400 to 700 nm) or not.
  6. Oct 25, 2009 #5
    I agree with jtbell here.

    If you don't know it already, find the equation that gives the wavelengths for hydrogen transitions, calculate the wavelengths for the transitions you are asking, and compare those to the wavelengths of visible light.
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