How did the Stern-Gerlach experiment provide evidence for quantized angular momentum?

The Stern-Gerlach experiment provided critical evidence for space quantization, confirming that the angular momentum of an atom is restricted to discrete orientations rather than being continuously distributed.12

In the experiment, a beam of silver atoms was passed through a nonuniform magnetic field. Because silver atoms possess a magnetic moment linked to their angular momentum, they behave like tiny compass needles. If angular momentum were not quantized, the atoms would have been deflected in a wide, continuous range of directions, creating a broad smear on the detection plate.132

Instead, the beam split into two distinct traces. This result demonstrated that the atoms' angular momentum could only take on two specific, discrete orientations relative to the magnetic field. This phenomenon, known as space quantization, supported the quantum mechanical view that physical properties like angular momentum are restricted to discrete values, a concept fundamental to the development of atomic theory following Niels Bohr's earlier work on quantized electron orbits.123