Quantum physics (quantum theory, quantum mechanics)

Stern-Gerlach experiment - 3
beam of Ag atoms (with electron in s-
state (l =0)) in non-uniform magnetic field
force on atoms: F = z· B z /z
results show two groups of atoms,
deflected in opposite directions, with
magnetic moments z = B
Conundrum:
• classical physics would predict a
continuous distribution of μ
• quantum mechanics à la Bohr-
Sommerfeld predicts an odd number
(2l +1) of groups, i.e. just one for an s
state
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