spins_unit_sg_experiment.ppt Pages 5-8

• After showing students that the energy stored in the rotation of the molecule to face in the direction of the loop is

$$U=\, -\vec{\mu} \cdot \vec{B} \; \; ,$$

• explain that, classically, experimentalists believed that the magnetic dipole moment would face in any random direction for each silver molecule. This would produce an even distribution of silver atoms on the firing screen since each molecule would be subject to a different force.

• The observed results were completely different; the silver atoms split into two discrete beams on the firing screen.
• The observed result implies the the magnetic dipole moment, and in turn the intrinsic angular momentum, can only face in two directions rather than any random direction. That is, the directionality of the intrinsic angular momentum and magnetic dipole moment are quantized.