The Lorentz-Lorenz Equation is a formula that relates the refractive index of a substance to the electronic polarizability of the constituent particles. But did you know who discovered the said equation first?
Physicist Ludvig Lorenz developed a mathematical equation to describe the refraction of light and the density of a pure transparent substance. Another physicist, Hendrick Lorentz, discovered the same equation almost ten years later.
Who was Ludvig Lorenz?
Ludvig Valentin Lorenz was born in Elsinore, Denmark in 1829. When he was just thirteen, Lorenz’s interest in physics piqued when he attended a lecture conducted by the Society for the Dissemination of Natural Science. The lecture made Lorenz decide he wanted to pursue further knowledge in mathematics and physics.
The Danish physicist started attending different courses at the Polytechnic College and the University of Copenhagen. He graduated as a polytechnic candidate in chemistry in 1852. However, Lorenz never received any formal education in physics, his preferred field. Through support from both government and private grants, Lorenz found himself in Paris in 1858 to further his studies on theoretical physics.
He specialized in theories of optics and elasticity, and in 1866 he was elected as a member of the prestigious Royal Danish Academy for Sciences and Letters. In the same year, he was appointed as a teacher at the Military High School in Copenhagen, where his tenure reached 21 years.
Lorenz tried to obtain a teaching position at the University of Copenhagen and the Polytechnic College but was unsuccessful. In 1887, he received a generous offer from the Carlsberg Foundation from Carlsberg Breweries. The foundation offered to pay the Danish physicist as an independent researcher to enable him to continue with his discoveries. (Source: ARXIV)
The Curious Case of Coincidence
Having initially adopted the mechanical models of light published by earlier scientists, the Danish physicist wanted to base a theory of light on directly observable quantities such as intensity, velocity, the direction of propagation, color, phase, and polarization plane.
This became Lorenz’s best-known work on optics, which resulted from systematic studies of refraction and its relation to the molecular state of a transparent medium. He then published his work in 1869, which was written in Danish, to which was known as the Lorenz equation.
Unknown to Lorenz, a 25-year-old Dutch scientist, Hendrik A. Lorentz, studied the same theory of light. The difference in the studies of the two scientists was their approach. The Danish Lorenz approached his study from a mechanical physics point of reference, while the Dutch Lorentz approached his study from an electromagnetic theory. Despite the difference in reference, the two deducted the same refraction formula.
At the time of his dissertation, the Dutch Lorentz was also unaware of Lorenz’s works, as Lorentz published his work in Dutch. They only found out about each other’s work when German translations of their papers were published in Annalen der Physik in 1880.
Their combined work became known as the Lorenz-Lorentz Equation. The equation spurred many experiments in molecular refractivity. It became an essential tool in the new physical chemistry.
Other scientists obtained valuable information on the bonds of chemical compounds, their constitution, and the size of molecules and ions. (Source: ARXIV)