Fresnel (the ‘s’ is silent) was Biot’s protégé. Arago collaborated with him on the polarisation of light, and used Fresnel’s work on wave theory to take revenge on Biot for sabotaging his own earlier work. Poisson’s work proved Fresnel right, but to Poisson’s own embarrassment, since he’d been sure Fresnel was wrong and was personally antipathetic to him. Fresnel collaborated with his close friend Ampère on research in electro-magnetism, and corresponded with Young, who was also interested in wave theory. Prosper Mérimée was his young cousin: it is unclear whether they crossed paths meaningfully.