Fabry–Pérot interferometer in the context of Interferometer

Marie Paul Auguste Charles Fabry ForMemRS (French: [maʁi pɔl oɡyst ʃaʁl fabʁi]; 11 June 1867 – 11 December 1945) was a French physicist working on optics. Together with Alfred Pérot he invented the Fabry–Pérot interferometer. He is also one of the co-discoverers of the ozone layer.

Jean-Baptiste Alfred Perot (French: [pəʁo]; 3 November 1863 – 28 November 1925) was a French physicist.

Together with his colleague Charles Fabry he developed the Fabry–Pérot interferometer in 1899.

In atomic physics, the fine structure describes the splitting of the spectral lines of atoms due to electron spin and relativistic corrections to the non-relativistic Schrödinger equation. It was first measured precisely for the hydrogen atom by Albert A. Michelson and Edward W. Morley in 1887. The explanation was first given by Niels Bohr in 1914, who suggested that the orbits of electrons in his Bohr model of the atom precessed due to relativistic effects. A successful relativistic formula was given by Arnold Sommerfeld in 1916. In the same work, Sommerfeld also introduced the fine-structure constant.

The Zeeman effect (Dutch: [ˈzeːmɑn]) is the splitting of a spectral line into several components in the presence of a static magnetic field. It is caused by the interaction of the magnetic field with the magnetic moment of the atomic electron associated with its orbital motion and spin; this interaction shifts some orbital energies more than others, resulting in the split spectrum. The effect is named after the Dutch physicist Pieter Zeeman, who discovered it in 1896 and received a Nobel Prize in Physics for this discovery. It is analogous to the Stark effect, the splitting of a spectral line into several components in the presence of an electric field. Also, similar to the Stark effect, transitions between different components have, in general, different intensities, with some being entirely forbidden (in the dipole approximation), as governed by the selection rules.

Since the distance between the Zeeman sub-levels is a function of magnetic field strength, this effect can be used to measure magnetic field strength, e.g. that of the Sun and other stars or in laboratory plasmas.