What is Mercury-vapor lamp?
[[File:High Pressure Mercury-vapor Lamps.JPG|thumb|Mercury-vapor lamps producing a blue light]] A '''mercury-vapor lamp''' is a kind of [[gas discharge lamp]]. It makes light from [[mercury (element)|mercury]]. The mercury atoms release [[ultraviolet]] and visible light. In some bulbs, the ultraviolet light shines on [[phosphor]]s which make white light from it, although not all mercury-vapor lamps use phosphors. The [[EU]] wants to ban them because they contain large amounts of mercury and are not efficient like [[fluorescent bulb]]s although mercury lamps last much longer. They are the bluish [[streetlight]]s. Depending on the quality of the bulb, age of the bulb, phosphor used, and other chemicals added to the mercury, the color of the light can vary from blue-white to green-white, to almost pure white. A green tint usually indicates an older bulb, although it doesn't necessarily mean that the bulb is about to burn out. The [[Metal-halide lamp|metal halide lamp]] is an improved version of the mercury vapor lamp that contains a metal [[halide]] (usually [[sodium iodide]]) in addition to the mercury. The metal halide produces orange light, which combines with the blue-white light from the mercury to produce a very pure white light. ==Related pages== *[[Sodium vapor lamp]] *[[Incandescent bulb]] {{science-stub}} [[Category:Lamps]]