GRIMALDI, FRANCESCO MARIA. - Jesuit, physicist, born in Bologna on 2 April 1613, died there on 28 December 1663.
He entered the religious life in 1632, and after teaching belles-lettres for 25 years, he devoted himself to the study of physics and collaborated with his confrere G. B. Riccioli on important works. Among his contributions are: studies on refraction and the dispersion and decomposition of white light into its elementary colors; the discovery of diffraction fringes, observed when a beam of light passes through a very narrow slit or a tiny hole (though also observed by Leonardo da Vinci); an innovative wave theory of light for his time; and the study of luminous spots. His principal works are: *Physico-mathesis de lumine, coloribus et iride, aliisque adnexis libri duo* (published posthumously, Bologna, 1665) and a *Selenographia* or selenographic chart, reproduced by Fr. G. B. Riccioli, who named the lunar features after GRIMALDI.