The author begins with an explanation of the physical characteristics of light waves, and then proceeds to survey the effects of light on art objects. Factors involved in the deterioration of objects include the intensity of the illumination, the time of exposure and the spectral distribution of the radiant energy. Further deterioration may depend on interaction of light with environmental factors such as relative humidity, temperature and the role of oxygen. Various ways of controlling harmful effects (such as elimination of UV, limited exposure to light) are suggested. See also <i>AATA 7-705 and 15-534. -- AATA