GRIMALDI, FRANCESCO MARIA. — Jesuit, physicist, born in Bologna on 2 April 1613, died there on 28 December 1663.
A religious from 1632, after teaching belles-lettres for 25 years he devoted himself to the study of physics and collaborated with his fellow religious G. B. Riccioli on important works. He is responsible for studies on the refraction and dispersion, or decomposition, of white light into the primary colors; the discovery of diffraction fringes, observed when a beam of light passes through an exceedingly narrow slit or a minute aperture (though also observed by Leonardo da Vinci); a wave theory of light, innovative for that period; and the study of lunar spots. His principal works are: Physico-mathesis de lumine, coloribus et iride, aliusque adnexis libri duo (posthumous, Bologna 1665) and a Selenographia o Tarsula selenografica, reported by Fr. G. B. Riccioli, who gave G.’s name to one of the lunar spots, in Almagestum novum (I, Bologna 1651, p. 204; V. also several observations by G. reported there on p. 754).