Neon lights are widely used in advertising[advertising?:advertising material cutting machine] signs. These signs are made of long, narrow glass tubes, and these tubes are often bent into all sorts of shapes. The tube of a neon light can spell out a word, for example. These tubes emit neon light in different colors.
The theory behind a neon light is simple. Inside the glass tube there is a gas like neon, argon or krypton at low pressure. At both ends of the tube there are metal electrodes. When you apply a high voltage to the electrodes, the neon gas ionizes, and electrons flow through the gas. These electrons excite the neon atoms and cause them to emit neon light that we can see. Neon emits red light when energized in this way. Other gases emit other colors of neon light.
