Faraday effect: between natural optical activity and the theory of electrons

In this work we describe and analyze the process of transition of the theoretical assumptions for the description and foundation of the Faraday effect, which took place in the second half of the 19th century. From the original scientific articles, published in the journals of the time, we tried to characterize how such efforts sought initial inspiration from Biot’s law of natural optical activity and from Fresnel’s theory of circular birefringence. Hence, the attempts at elastodynamic description of the phenomenon emerged. The followers of Maxwell’s electromagnetic work, in turn, promoted the transition to its electromagnetic foundation and, as we have indicated, such an approach only became viable with the ionic hypothesis of matter and the discovery of the electron, at the end of the century.

Keywords:
circular birefringence; natural optical activity; magnetic optical activity; ionic hypothesis; electron