OPTICAL

adj. 1 of sight; visual. 2 a of or concerning sight or light in relation to each other. b belonging to optics. 3 (esp. of a lens) constructed to assist sight or on the principles of optics. optical activity Chem. the property of rotating the plane of polarization of plane-polarized light. optical art a style of painting that gives the illusion of movement by the precise use of pattern and colour. optical brightener any fluorescent substance used to produce a whitening effect on laundry. optical character recognition the identification of printed characters using photoelectric devices. optical disc see DISC. optical fibre thin glass fibre through which light can be transmitted. optical glass a very pure kind of glass used for lenses etc. optical illusion 1 a thing having an appearance so resembling something else as to deceive the eye. 2 an instance of mental misapprehension caused by this. optical microscope a microscope using the direct perception of light (cf. electron microscope). optically adv.