noun.
That branch of physical science which treats of the nature and properties of light, of the theory of colors (chromatics), of the change which light suffers either in its qualities or in its course when refracted or transmitted through bodies (dioptrics), when reflected from their surfaces or when passing near them (catoptrics), of the structure of the eye and the laws of vision, and of the construction of instruments of introspection, as telescopes, microscopes, etc.