A Modern Approach to Quantum Mechanics · Problem 3.21

Time Evolution — John S. Townsend

Physics — Quantum Mechanics · angular-momentum-quantization

Problem

Introduce an angle

\theta

defined by the relation

\cos\theta = J_z/|\mathbf{J}|

, reflecting the degree to which a particle's angular momentum lines up along the

z

axis. What is the smallest value of

\theta

for (a) a spin-

\frac{1}{2}

particle, (b) a spin-1 particle, and (c) a macroscopic spinning top?