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MERLOT II


    

Learning Exercise


Material: Visual Quantum Mechanics
Submitted by: Terry Bradfield on Sep 05, 2001
Date Last Modified: Sep 05, 2001
Title: Virtual Lab on the Visible Spectrum of Hydrogen.
Description: This is a worksheet that makes use of the emission and absorption applets for the visible spectrum of hydrogen within the Visual Quantum Mechanics Website. It is designed to be used in a survey course for non-science majors.
Type of Task: Individual, Unsupervised
Time Required 30 min
Topics: Bohr Model of the Hydrogen Atom, Atomic Spectroscopy
Course: General Physical Science
Categories:
Learning Objectives: Students will explore the connection between discrete electron energy levels and the characteristic visible spectrum of hydrogen.
Technical Notes: The applets used in this assignment require a Shockwave-enabled browser.
Text of Learning Exercise:





Virtual Lab Assignment No. 3




Virtual Lab No. 3:  The Visible Spectrum of Hydrogen.




Introduction


In this lab we will see how Bohr's model of the hydrogen atom can account
for its observed spectrum.  Your goal is to find the orbit transitions
that produce the four visible lines in the spectrum for both the emission
and absorption cases.  The applets for this lab can be found at the
links  http://phys.educ.ksu.edu/vqm/html/emission.html
for the emission spectrum, and  http://phys.educ.ksu.edu/vqm/html/absorption.html
.  Instructions for using the applet are included in this link. 
For those who don't want to calculate orbit energies themselves, you can
determine these by using the applet located at  http://home.a-city.de/walter.fendt/phe/bohrh.htm
. The energy of the electron in the currently selected orbit is given in
the lower right hand corner of the applet window.  Values in joules
and electron volts are given, you will  need the latter unit value
for this lab.


Procedure





  1. The first step is to construct a table showing the electron energy in each
    of its possible orbits. Although in reality there are an infinite number
    of possibilities, to investigate the visible spectrum we need only consider
    values from n = 2 to n = 6.  The energy of the electron in each orbit
    can be found either using the formula ,
    or by using the Bohr
    theory of hydrogen applet
    .












































  2. Principal Quantum Number nElectron Energy (in eV)
    n = 1 

    n = 2

    n = 3 

    n = 4

     

    n = 5

     

    n = 6

     



  3. Next, load the emission
    spectrum applet
    . This will open in a new browser window. Move the mouse
    over one of the spectrum lamps; when you do so, the name of the material
    in the lamp will appear next to it.  Select the hydrogen lamp by clicking
    and dragging it to the spectrum lamp sockets. When the lamp is placed in
    the socket, the visible part of the hydrogen spectrum will appear at the
    top of the applet window.



  4. Follow the instructions in the applet to add each of the energy levels
    in your table to the energy level diagram in the applet. Since the graph
    scale is fairly coarse, you won't be able to match them exactly, but try
    to get as close as you can.



  5. With energy levels in place, you are ready to begin experimenting with
    transitions. When you enter a transition in the diagram, the spectral line
    to which it corresponds will appear in the section below the hydrogen spectrum,
    if its wavelength lies in the visible range, otherwise, nothing will happen.
    If you need to remove a transition, you can do so by dragging it off the
    graph.



  6. Once you have obtained all four of the visible lines in the hydrogen spectrum,
    complete the table below.










































  7. Spectral LineStarting Orbit NumberEnding Orbit No.
    Red  
    Blue  
    1st Violet  
    2nd Violet  



  8. Next, load the absorption
    spectrum applet
    . Add the electron energy levels to it in the same fashion
    as for the emission applet. Experiment with transitions until you duplicate
    all the absorption lines and complete the table below.












































  9. Absorption Spectrum Transition for Hydrogen
    Spectral LineStarting Orbit No.Ending Orbit No.
    1st  
    2nd  
    3rd  
    4th  



    Questions


    1.  Do you see any patterns in the transitions that generate the emission
    spectrum of hydrogen?  If so, what are they?

     

     

     

     

     

    2. How do the transitions that generate the absorption spectrum compare
    with those that generate the emission spectrum?

     




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