Pieter Zeeman observed changes in emitted light when its source was placed in a magnetic field. Resolving the components and their wave polarization connected the spectral pattern with the direction of observation. The magnetic field changes atomic energy levels, while selection rules determine which polarized components are visible. Comparing observations along and across the magnetic field therefore tests more than a simple increase in line width: it connects the Zeeman effect to both atomic structure and experimental geometry.[ref]
On the Influence of Magnetism on the Nature of the Light Emitted by a Substance (Part I) by Pieter Zeeman. Original observation and spectral changes
[ref]A physicist.[ref]
https://www.nobelprize.org/nomination/archive/show.php?id=7221. Biographical identity and professional specialization
Portrait of Pieter Zeeman
. Source. The Zeeman effect connects a laboratory magnetic field to the frequencies and wave polarization of light emitted by chemical atoms. Its experimental history makes the viewing direction and spectral resolving power essential to the inference.
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Pieter Zeeman (1865-1943) was a Dutch physicist best known for his discovery of the Zeeman Effect, which describes the splitting of spectral lines in the presence of a strong magnetic field. This phenomenon occurs because the energy levels of atomic electrons are affected by the magnetic field, resulting in the observed splitting of light into different frequencies.
