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P > PHOTO RESIST - Pg. 195

PHYSICAL CHARACTERISTICS oven-drying varnishes. They are also used as impregnating agents and as components of paints, varnishes, lacquers, and adhesives. PHOTODIODE A semiconductor device used in light-wave sys- tem to convert light energy to electrical energy. PHOTOGRAPHIC REDUCTION DIMENSION Dimensions, e.g., the distance between lines or between two specific points on the artwork master, used to indicate to the photographer the extent to which the artwork master is to be photographically reduced. (The value of the dimensions refers to the 1:1 scale and must be speci- fied.) PHOTON The photon is the quantum (an indivisible energy unit) of the electromagnetic field. It has no electric charge, no rest mass, no magnetic field, and a long lifetime. In a vacuum, it travels at the speed of light. PHOTO RESIST A photosensitive plastic coating material that hardens when exposed to ultraviolet light and resists etching solu- tions.