describes: a quantity which has only certain separated or discrete values, as opposed to a continuous range of values. [P10.3]
appears: often in quantum physics but not in classical physics (except for the allowed frequencies of standing waves - from which the idea of quantum physics evolved). [P8.2]
is exemplified: in the Bohr model for atomic hydrogen, by the atomic electron having only certain values for the magnitude of its angular momentum about the nucleus (Bohr quantization condition), which leads also to quantized energy levels for the atomic electron's bound states. [P8.2, P8.3]
is also exemplified: when electromagnetic radiation interacts with matter, by the energy transfers being quantized in terms of photons (quantum theory of electromagnetic radiation). [P8.2]
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