Augustin Jean Fresnel (1788-1827), French physicist. Fresnel qualified as an engineer, but was temporarily removed from his government post in 1815 for supporting the Royalists against Napoleon. At this time he grew interested in the problem of light and conducted experiments that Young had done a decade earlier, and researched interference and polarisation effects. He also showed that, to explain the effects, light must be in the form of transverse waves, as Young & Huygens had suggested, rather than longitudinal waves, like sound. Fresnel also applied his skills to the development of lenses for light-houses.