Virtual Lab on the Visible Spectrum of Hydrogen.
Virtual Lab No. 3: The Visible Spectrum of Hydrogen.
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
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.
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.
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.
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.
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
Once you have obtained all four of the visible lines in the hydrogen spectrum,
complete the table below.
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.
|Principal Quantum Number n||Electron Energy (in eV)|
|n = 1|
|n = 3|
|Spectral Line||Starting Orbit Number||Ending Orbit No.|
|Spectral Line||Starting Orbit No.||Ending Orbit No.|
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?