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Joined 2026-09-21 Message
Incoming links: Hendrik Antoon Lorentz
Nobel Prize in Physics in 1902 2026-10-18
Hendrik Antoon Lorentz and Pieter Zeeman shared the award equally for research on magnetic influences on electromagnetic radiation.[ref]
The Nobel Prize in Physics 1902 by Nobel Prize Outreach. Official summary: laureates, prize shares and motivation
The Zeeman discovery experiment of 1896 connects this award to changes in spectral lines. Zeeman discovery experiment of 1896 2026-10-18
In August 1896, Pieter Zeeman observed broadened sodium spectral lines at Leiden, initially without resolved components. His lecture describes a slit and concave diffraction grating, then compares the broadening with the sodium doublet separation: about one thirtieth, roughly ångström. This supplied a spectral reference scale, not an absolute magnetic field calibration. Later cadmium photographs displayed resolved transverse triplets and axial doublets.[ref]
Light Radiation in a Magnetic Field by Pieter Zeeman. Pieter Zeeman, Light Radiation in a Magnetic Field, Nobel lecture delivered May 2, 1903; University of Maryland mirror PDF pp. 2–3, paragraphs beginning “In August, 1896”, “The change was however very small” and the cadmium photograph discussion
The fuller report specifies a concave diffraction grating of ten-foot radius with 14,438 lines per inch, an adjustable slit and a micrometer eyepiece with vertical crosswire. Salt in a flame between electromagnet poles supplied the sodium spectral lines. Repeated switching broadened and restored them. To test changes in flame temperature or vapour density, Pieter Zeeman examined photon absorption through a heated porcelain tube with water-cooled glass windows. The arc lamp was displaced from the magnet and its light redirected by a mirror to avoid disturbing the arc. Rotating a narrower tube made the absorption spectral lines equally broad at different heights; the magnetic field still broadened their whole length.[ref]
For the axial test, pierced electromagnet poles let the light travel along the magnetic field. A quarter-wave plate and polarizer selected one broadened edge; rotating the analyser by or reversing the magnet current exchanged the visible edge. The crosswire made its displacement detectable. This tested electromagnetic polarization as well as line width. For its rough estimate the report compared each side's widening with the sodium doublet separation, obtaining about one fortieth, and stated an approximate magnetic field intensity in historical units. These passages give no absolute field-calibration procedure; the inferred charge-to-mass ratio was explicitly a first approximation.[ref]
On the Influence of Magnetism on the Nature of the Light Emitted by a Substance (Part II) by Pieter Zeeman. Pieter Zeeman, On the influence of magnetism on the nature of the light emitted by a substance, Part II, §§14, 20 and 23, printed pp. 10, 16–18; scan is a corrected reprint as its footnote to §24 explains
Hendrik Antoon Lorentz's charged-oscillator theory connected the observed splitting to moving electric charge. In modern language, a line-position measurement needs a wavelength or frequency calibration and an independent magnetic field calibration before it determines a magnetic dipole moment. Resolving the individual components adds the transition information used in the worked example below.