Early 20th century
- 1905 - Albert Einstein explained the photoelectric effect.
- 1905 - Einstein presented the special theory of relativity,
in which the speed of light is independent of the motion of its
source and constant in any inertial frame of reference.
- 1913 - Neils Bohr's theory of the atom, explains the Balmer,
Rydberg and Ritz formulas of simple spectra.
- 1913 - Johannes Stark discovered the Stark effect, the splitting
of spectral lines in an electric field.
- 1923 - Compton explained x-ray scattering.
- 1925-7 - Quantum theory of the atom, developed by many people
including Wolfgang Pauli (exclusion principles), Werner Heisenberg (uncertainty principle),
Erwin Schrödinger (wave equation), Louis de Broglie, Max Born
(wave function as probability), Jordan, and Paul A M Dirac
(relativistic wave equation).
- 1928 - Neils Bohr proposed the Complementarity Principle.
- 1930 - Gerlach and Scweitzer introduced the ratio method for
- 1936 - Thanheiser and Heyes used photocells to measure intensities.
- 1942-9 - Giulio Racah presented his formulation of the angular components of Schrödinger's equation.
- ~1945 - P M Duffieux and R K Luneberg introduced
Fourier methods to optics.
- 1947 - Willis E Lamb discovered the Lamb shift.
- 1947 - Dennis Gabor developed holography.
- 1948 - Sin-itiro Tomonaga, Julian S Schwinger and
Richard P Feynman developed quantum electrodynamics
- 1949 - D R Bates and Agnette Damgaard presented
an approximate solution to the radial part of Schrödinger’s equation.
- 1950 - A Kastler caused population inversion in excited atoms.
First published on the web: 15 December 1999.