A superposition of waves with one predominant wave number k, but with several other wave numbers near k. Wave packets are useful for the analysis of scattering in quantum mechanics. Concentrated packets of waves can be used to describe localized particles of both matter and photons. The Heisenberg uncertainty principle can be derived from a wave-packet description of entities in quantum mechanics. The motion of a wave packet is in accord with the motion of the corresponding classical particle, if the potential energy change across the dimensions of the packet is very small. This proposition is known as Ehrenfest's theorem, named after the Dutch physicist Paul Ehrenfest (1880–1933), who proved it in 1927.
Subjects: Chemistry — Physics.