Glossary / History of physics
Correspondence principle
The principle that quantum results must agree with classical physics in the limit of large quantum numbers — large objects and high energies.
Not knowing the right form of the new quantum rules, Bohr reasoned that they should at least reproduce the old physics where the old physics worked, and used this to estimate the intensity and polarisation of spectral lines. In a 1920 paper he called the idea "correspondence"[1].
It is a way of building a theory from conditions the answer must satisfy, without knowing the answer itself, and it served as scaffolding when Heisenberg created matrix mechanics in 1925.
Related terms
- Bohr modelThe 1913 model in which electrons circle only on certain orbits and emit light of definite energy when jumping between them.
- Old quantum theoryThe theories of roughly 1900 to 1925, from Planck onwards, that explained phenomena by adding quantum conditions on top of classical physics.