Faraday and the Electromagnetic Theory of Light

Abstract

Michael Faraday (1791-1867) is probably best known for his discovery of electromagnetic induction, his contributions to electrical engineering and electrochemistry or due to the fact that he was responsible for introducing the concept of field in physics to describe electromagnetic interaction. But perhaps it is not so well known that he also made fundamental contributions to the electromagnetic theory of light. In 1845, just 170 years ago, Faraday discovered that a magnetic field influenced polarized light – a phenomenon known as the magneto-optical effect or Faraday effect. To be precise, he found that the plane of vibration of a beam of linearly polarized light incident on a piece of glass rotated when a magnetic field was applied in the direction of propagation of the beam. This was one of the first indications that electromagnetism and light were related. The following year, in May 1846, Faraday published the article Thoughts on Ray Vibrations, a prophetic publication in which he speculated that light could be a vibration of the electric and magnetic lines of force.