Quantum physics (quantum theory, quantum mechanics)

wave-particle duality:
Summary
• objects behave like waves or particles, depending on
experimental conditions
• complementarity: wave and particle aspects never manifest
simultaneously
Spin:
• results of Stern - Gerlach experiment explained by
introduction of “spin”
• later shown to be natural outcome of relativistic invariance
(Dirac)
Copenhagen interpretation:
• probability statements do not reflect our imperfect
knowledge, but are inherent to nature – measurement outcomes
fundamentally indeterministic
• Physics is science of outcome of measurement processes -- do
not speculate beyond what can be measured
• act of measurement causes one of the many possible outcomes
to be realized (“collapse of the wave function”)
• measurement process still under active investigation – lots of
progress in understanding in recent years
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