In-class group activity 10: A Stern Gerlach Experiment

Use an on-line simulation from the University of Colorado PhET group to carry out a Stern-Gerlach Experiment.  
Link to the simulation http://phet.colorado.edu/en/simulation/stern-gerlach.  Click "Run Now!".

Open a Microsoft Word document to keep a log of your procedures, results and discussions.

• Explore the interface. There are some non-obvious controls.

  • Grab the dial on the angle indicator to rotate the magnet.

  • Select up or down for which spin the magnet lets through.

  • Spin orientation controls the spin of the atoms coming out of the source.

  • Turn on the Sound to hear the atoms popping out the source and through the magnets

You can perform experiments with one, two or three magnets.  If you choose “up” to open the exit hole for the spin-up particles and block the hole for the spin-down particles, you have a spin filter as described in the notes.

• Work with one spin filter.

  • Let the spin filter point in the positive z-direction.  For the +z, +x, -z, and random xz spin orientation monitor the percentage of particles emerging from the filter.

  • Describe your observations when only a few particles have entered the magnet, and when a large number of particles have entered the magnet.

  • Repeat with the spin filter pointing at +30^o

  • Repeat with the spin filter pointing at -30^o.

•  Work with two spin filters.

  • Let the second spin filter point in the positive z-direction.  Change the orientation of the first spin filter and monitor the percentage of particles passing through both filters for the +z, +x, -z, and random xz spin orientation.

  • Fill in the table below after a large number of particles have entered the magnet.

• Work with three filters.

  • Create an experiment that would be the quantum analog of the classical experiment described below.

  • Take a box of pennies and shake it.  Put the box down, open it up and remove the “tails”.

  • Now close the box and vigorously turn it on its side.

  • Open the box and take out the “tails”.

  • Close the box and vigorously turn it back to its original position.

  • What percentage of the original pennies are now in the “head” state?

  • Are quantum pennies different from classical pennies?