Optical properties relating to the amount of light or other radiation that can be reflected by an item. Rough surfaces reflect in a multitude of directions, and such reflection is said to be diffuse. Smooth, brightly polished or glossy surfaces reflect clearly and sharply at the same angle to the surface as the angle at which the light or heat contacted the surface. Reflectometers are instruments used for measuring the luster or sharpness of reflection of a finished surface.