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:
Bohr Model of the Hydrogen Atom, Atomic Spectroscopy
Students will explore the connection between discrete electron energy levels and the characteristic visible spectrum of hydrogen.
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.
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.
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.
Principal Quantum Number n
Electron Energy (in eV)
n = 1
n = 2
n = 3
n = 4
n = 5
n = 6
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 graph.
Once you have obtained all four of the visible lines in the hydrogen spectrum, complete the table below.
Starting Orbit Number
Ending Orbit No.
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.
Absorption Spectrum Transition for Hydrogen
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?