Newton argued that light is composed of particles or corpuscles, which were refracted by accelerating into a denser medium. He verged on soundlike waves to explain the repeated pattern of reflection and transmission by thin films (Opticks , Props. 12), but still retained his theory of 'fits' that disposed corpuscles to be reflected or transmitted (). However, later physicists favoured a purely wavelike explanation of light to account for the interference patterns and the general phenomenon of diffraction . Today's quantum mechanics , photons , and the idea of wave–particle duality bear only a minor resemblance to Newton's understanding of light.