Substance that produces light when excited by some form of energy, usually an electron beam. Phosphor is used for coating the inside of a monitor (the cathode ray tube). A thin layer of phosphor is arranged in a pattern of tiny dots on the inside of the screen and produces an image when scanned by the picture beam. In a colour screen there are three tiny coloured phosphor dots (coloured red, green and blue) arranged in a group; the different colours you see displayed are a mix of the light from the three dots.
