What is Gas discharge lamp?
[[Image:Germicidal UV discharge tube glow.jpg|thumb|250px|[[Germicidal lamp]]s are simple low pressure mercury vapor dischargers]] '''Gas discharge lamps''' are a family of artificial light sources (or [[lamp]]s). These lamps produce light by sending [[electricity]] through an [[ionization|ionized]] [[gas]]. Most of these lamps use a [[noble gas]] (often [[argon]] or [[neon]] gas), or a combination of noble gases, but they often contain other materials, such as [[Mercury (element)|mercury]], [[sodium]] or [[metal]] [[halide]]s. The gases in these lamps are ionized in operation. This means that there are free [[electron]]s. When an [[electric current]] is sent through the gas, electrons collide with atoms of the gas and the metals. This will mean that some reach a higher energy state. When they fall back into the lower energy state, they will emit the energy in the form of [[light]]. The [[fluorescent lamp]] is probably the best known gas discharge lamp. [[Sodium vapor lamp]]s are commonplace as [[streetlight]]s. [[Neon lamp]]<nowiki/>s are used in advertising. Gas-discharge lamps have a long life and a high [[Energy efficiency|efficiency]], but they are more complicated to manufacture, which makes them more expensive to buy than incandescent lamps. Due to their greater efficiency, gas-discharge lamps replaced [[incandescent light bulb]]s for many purposes in the late 20th century. Early in the 21st century, [[Light bulb|light-emitting diodes]] improved, with even higher efficiency. They began to replace some gas discharge lamps. {{stub}} [[Category:Lamps]]