Question: when is light given off in a neon light

title: Neon lighting
text: Neon lighting consists of brightly glowing , electrified glass tubes or bulbs that contain rarefied neon or other gases . Neon lights are a type of cold cathode gas - discharge light . A neon tube is a sealed glass tube with a metal electrode at each end , filled with one of a number of gases at low pressure . A high potential of several thousand volts applied to the electrodes ionizes the gas in the tube , causing it to emit colored light . The color of the light depends on the gas in the tube . Neon lights were named for neon , a noble gas which gives off a popular orange light , but other gases and chemicals are used to produce other colors , such as hydrogen ( red ) , helium ( yellow ) , carbon dioxide ( white ) , and mercury ( blue ) . Neon tubes can be fabricated in curving artistic shapes , to form letters or pictures . They are mainly used to make dramatic , multicolored glowing signage for advertising , called neon signs , which were popular from the 1920s to the 1950s . 

Answer: answer: Neon lighting consists of brightly glowing, electrified glass tubes or bulbs that contain rarefied neon or other gases.  A high potential of several thousand volts applied to the electrodes ionizes the gas in the tube, causing it to emit light.
answer: A high potential of several thousand volts applied to the electrodes ionizes the gas in the tube, causing it to emit colored light.