French physicist who informed Fresnel, who was working on a wave theory of light, of Young's work on the subject. Arago stopped his collaboration when Fresnel adopted Young's unconventional suggestion that light consisted of transverse waves. In 1811, Arago showed that the state of polarization changes when light passes through quartz. With Biot he also studied refraction in gases. Arago also performed experiments which failed to detect the motion of the Earth with respect to the ether.

Arago was director of the Observatoire de Paris from 1843-1853.

Biot, Fresnel, Young

Additional biographies: MacTutor (St. Andrews), Bonn