wang
(Wang)
#1
(1)With a strong magnetic field, the signal of the individual atoms emerging from SG is
centered sharply on two outcomes, which correspond to opposite values of the magnetic
moment. The detectors counting the number of atoms for each outcome are never triggered
simultaneously. Thus each silver atom must have + or−value for the spin.
(2)The observed values of spin are along thez-axis (which is the N-S direction of the magnet
in SG), and take only two possible values,
Sz=± ̄h/ 2 (2.23)
For a given atom entering the SG apparatus, it is impossible to predictwhether the outcome
will be + or−. The SG apparatus on spin is precisely analogous to the birefringentplate for
the photon. The analog of a polarizer at angleθfor the photon is an SG apparatus rotated
by an angleθwith respect to thez-axis, and with one of the two outgoing beams blocked.
(3)The following experimental set-ups again exemplify the quantum behavior of the spins.
Figure 6: The Stern-Gerlach experiment with multiple SG separators
The first set-up shows that a spin prepared in stateSz= + ̄h/2 remains in stateSz=
+ ̄h/2. The second set-up shows that a spin prepared in stateSz= + ̄h/2 yields with equal
