This sequence of activities gives students a chance to practice a variety of calculations for a specific system: a quantum particle confined to a ring. In particular, these activities help students to see that all of the calculations that they have done previously in the Spins and Waves courses can be applied to these new systems. In addition to the main goal(s) for each activity, they all provide an opportunity for students to deal with degeneracy and to move between the different representations/notations that they have used (bra-ket notation, matrix notation, and wave function notation).

Typically, the first few activities are done in class and the rest are incorporated into the homework using these or similar problems (wiki version, cfqmringhomeworkcombined.pdf).

• Energy and Angular Momentum for a Particle on a Ring
  • Students calculate probabilities for energy and angular momentum for a particle confined to a ring in Dirac “bra-ket” notation, matrix notation and wavefunction notation. One of the main purposes of this activity is to help students see the parallel between similar calculations in these three representations.
• Time Dependence for a Particle on a Ring
  • Students calculate probabilities for energy, angular momentum and position as a function of time. The main purpose of this activity is to help students build an understanding of when they can expect a measurement probability to be time dependent.
• Superposition States for a Particle on a Ring
  • Students are asked to calculate probability for energy, angular momentum and position on a wavefunction that is not easily separated into eigenstates of the system.
• Expectation Values for a Particle on a Ring
  • Students calculate the expectation values for energy and angular momentum as a function of time.

The ring activities can also be sequenced with activities that ask the students to do similar calculations for a particle confined to sphere or for the hydrogen atom. For example:

• Quantum Calculations on the Hydrogen Atom
  • Students calculate probabilities and expectation values for energy and angular momentum for a hydrogen in a linear combination of $\vert n\ell m\rangle$ states.
• Probability of Finding an Electron Inside the Bohr Radius
  • Students work in small groups to calculate the probability that an electron in a hydrogen atom will be within one Bohr radius of the center.