« The wavelength of light as Thomas Young invented it »

Auteur : Olivier Morizot

Publié dans Archives for History of Exact Sciences vol. 80, Issue 1, 2026.

Editeur : Springer Nature

DOI : https://doi.org/10.1007/s00407-026-00387-7

Abstract
This paper documents Thomas Young’s invention of a concept which he alternately
refers to as the “magnitude”, “breadth”, “interval”, or “length of an undulation” of light.
First, the paper highlights that Young was first to link some concept of a wavelength
to a theory of optics and to assign a precise value to this length for each component of
the colour spectrum. Then, it sets out an explanation of how Young made up these values,
comparing them with the material previously available within Newton’s Opticks.
Finally, it examines the reasons why Young introduced an optical wavelength into his
theory of light, insofar as these reasons might shed light on why he was first to do so.