A system with uplight will improve the luminance of the ceiling and vertical surfaces, such as blackboards and computer screens. Indirect illumination will also minimize shadows. Providing some downlight with perforated holes or a lens in the bottom of the lighting fixture will make people think the atmosphere is brighter. They will feel more comfortable. Although fluorescent systems are probably the most popular for classrooms, other light sources may be appropriate for various areas.
Incandescent lamps are the primary source of illumination in most homes.
Fluorescent lamps produce light by activating selected phosphors on the inner surface of the bulb with ultraviolet energy generated by mercury arc. HID sources include mercury vapor, metal halide, high pressure sodium and low pressure sodium. HID is also a point source, which provides the opportunity for better light control. Specular Reflectors Specular reflectors may also be used for classroom applications. Specularity is the measure of a surface's ability to reflect all of the light at the inverse of the angle at which it is received.