Overview
Prior to beginning this assignment you should have read through page 26 of the Lindley book. This should give you a solid understanding of the basic Stern-Gerlach experiment. Your writing assignment will extend what you have read by delving deeper into variations of the Stern-Gerlach experiment and allowing you to do some exploring on your own.
For this assignment you will conduct a series of experiments using a simulated Stern-Gerlach apparatus (called SPINS). You will be able to run the SPINS program directly from this Launcher Package, but it is also available as a Java applet (which requires a Java-enabled browser) at
http://www.physics.orst.edu/~mcintyre/ph425/spins/spinsapplet.html. Some instructions on how to use the applet are available at http://www.physics.orst.edu/~mcintyre/ph425/spins/spinhelp.html. This is a good place to look if you have any trouble running the simulations in this Launcher Package.
Your paper should begin with a brief introduction to the Stern-Gerlach experiment and the idea of electron spin. For each experiment you should have at least one paragraph which will include the following items:
- a description of the experimental setup (in words),
- a description of the results of the experiment,
- comments on the results and answers to any questions listed in this handout.
You do not need to show any calculations that you perform. You need only give the results (I will be able to tell if you did the calculation correctly). Also, it is unnecessary for you to include diagrams in your paper. You should be able to clearly describe the experimental setup in words. If you feel you must include a diagram then you should ask me for help. Finally, you should end your paper with a concluding paragraph that summarizes your findings and highlights any interesting results that you found.
The main point of these experiments is to illustrate that quantum mechanics forces us to confront two apparent problems:
- measuring the state of a system seems to alter the state of the system, and
- the quantum state of a system (with respect to some particular measurement) does not seem to be well-defined until the measurement is actually performed.
These two ideas are intimately tied together. The Stern-Gerlach experiment forces us to confront these issues head-on.
Use the navigation menu on the left to conduct each simulated experiment. Make sure to read the text that accompanies the simulation as this is where you will find some important questions that you will need to address in your paper. Double-click on the green arrow when you are ready to run the simulation. Below is a description of the various components and controls used in each simulation.
- Electron Gun: The electron gun (always on the left side of the simulation) creates a beam of electrons. The electrons in the beam may be prepared in a particular quantum state, or they may be in a random mixture of different quantum states.
- Analyzer: The Stern-Gerlach analyzer separates the electron beam into two beams, one consisting only of electrons with spin up along the designated axis and the other consisting only of electrons with spin down along that axis. Clicking the letter in the center of the analyzer (i.e. X, Y, Z) allows you to change the axis along which the spin is measured.
- Counter: The counter simply counts the number of electrons that it receives.
- Go Button: This button starts the simulation by producing a continuous electron beam from the Electron Gun.
- Stop Button: This button stops the simulation by shutting off the Electron Gun.
- Reset Button: This button zeros the counters and resets the simultation to its original state.
- Step Button: This button causes the Electron Gun to fire a single electron so that the results of the simulation can be viewed one electron at a time.
- Step 1000 Button: This button causes the Electron Gun to fire a burst of 1000 electrons all at once. This is a good way to quickly build up lots of data and get good statistical results.
f you run into any trouble ask Dr. T!