Angular Momentum in Quantum Mechanics: Spin Indepth » Quantum_projection_of_S_onto_z_for_spin_half_particles
Visualization of a fermion’s spin angular momentum in the “spin-up” and “spin-down” orientations along the z-axis. Notice how the vector sweeps out a circle in the xy-plane. This causes the x & y components of the spin-angular momentum to be smeared all along this circle
