Fresnel, Augustin Jean
Fresnel, Augustin Jean (1788-1827), a French physicist and engineer who specialized in the study of optics. His experiments firmly established the wave theory of light. He also performed experiments on the polarization and diffraction of light. As an engineer, he developed a type of lens, now known as the Fresnel lens, to replace mirrors in lighthouse lamps. The lens, which has a series of concentric, curved ridges instead of the usual smoothly curved face, is still used in lighthouses and is also used in the viewing systems of many 35-mm cameras. Fresnel was admitted to the French Academy in 1823.