|fresnel (ˈfreɪnɛl, French frɛnɛl)|
|a unit of frequency equivalent to 1012 hertz|
|[C20: named after Augustin Jean Fresnel (1788--1827), French physicist]|
French physicist whose investigations of the interference, diffraction, and polarization of light helped establish the theory that light moves in a wavelike motion. Fresnel also made great contributions to the field of optics, including the development of a compound lens for use in lighthouses.