Neon lighting works in the same way as the fluorescent lights we are all familiar with as a part of our everyday life.
A ‘neon light’ is simply a narrow glass tube with metal electrodes at each end filled with an inert gas. Light is created by applying a voltage across the electrodes. This causes electrons to be emitted from one of the electrodes and move at high speed toward the other. Light is produced along the tube when the current of fast moving, high energy electrons ‘collide’ with atoms of the inert gas*.
The gas must be chemically inert and not affected by interacting with high energy electrons. The development and commercial use of neon lighting followed the isolation and production of the chemically inert noble gases helium, neon, argon and xenon(particularly neon) early last century.
To create a neon sign a glass tube is bent into the required shape by a glass blower – the electron flow will follow and light up the shape of the tube. The inner surface of the tube is coated with a phosphor material (if required), electrodes are attached and the tube is filled with the selected gas and sealed. More than one tube can be used to produce a multi-coloured sign.
Different colours are obtained by using different gasses or gas mixtures in the tube (neon for red; mercury vapour for blue) and by coating the inside of the tube with a thin film of a phosphor material that interacts with the light produced by the flow of electrons to produce light of a particular colour. This process is called fluorescence**!
For the science-minded . . .
*When a fast moving electron collides with an inert atom the electron loses some of its energy to the atom and puts it into an unstable ‘excited state’. The excited atom promptly returns to its normal state by releasing energy as light. The colour of this light is a property of the element and varies from one element to another.
**A phosphor is a substance which can be excited by short wavelength, high energy light to an excited state where it promptly releases longer wavelength, lower energy light. The colour of the emitted light is a property of the phosphor coating.