Wave-particle duality
Light behaves as a wave in some experiments, spreading and interfering, and as a stream of discrete particles in others, arriving one packet at a time. Electrons and other matter do the same, as the double-slit experiment shows: send them through one at a time and they still build up an interference pattern. Quantum mechanics does not resolve this by declaring one description correct. It supplies a single mathematical object whose predictions match the wave behaviour in one setup and the particle behaviour in another.
Why it matters
It marks the point where quantum objects stop fitting either classical category, which is why the theory needs its own vocabulary rather than a repaired version of the old one.
Also written: wave-particle duality, duality
Where it comes up
Read about Wave-particle duality on Wikipedia
Sources
- Wave-particle duality English Wikipedia
- Double-slit experiment English Wikipedia
- Photoelectric effect English WikipediaThe effect Einstein explained in 1905 by treating light as discrete quanta.
