splamorprecession.ppt (Slide 4)

• This lecture is best performed following the Ehrenfest's Theorem lecture.
• Slide 4 shows the expectation value of the general spin operator $\vec{S}$ spinning about the x-y plane with a constant magnitude in the z-direction (as long as $\theta$ is constant). This rotation of the expectation value is called “Lamor Precession” and the frequency at which the expectation value rotates is called the “Lamor Frequency.”
• Note that this rotation is a direct consequence of the fact that the direction in which the particle is spin-up is changing with time.

Providing the slides in a handout form is often beneficial for students so they can discuss and review the calculations at a later time and at their own pace.