Neon & Fluorescents lights

1. Neon & Fluorescents lights

2. How does Neon lights work? • A neon tube contains a gas that emits when an electrical current passed through it. • Neon itself natural produces a signature red glow, but the colour of the light can be augmented by the addition or substitution of argon, krypton, phosphorus, xenon, mercury and helium among others.

3. How do Fluorescent lights work? • A fluorescent light does not have the usual glowing filament of an incandescent bulb, but instead contains a mercury vapor that gives off ultraviolet light when ionized. • “Neon” light can be differentiated from fluorescents by the fact that the gas inside the fluorescent bulbs doesn’t emit light by itself but cause the coating of phosphor on the inside of the bulb to be illuminated by the particles stimulation, producing visible light.

4. Principles of operation. • The fundamental means for conversion of electrical energy into radiant energy in a fluorescent lamp relies on inelastic scattering of electrons. An incident electron collides with an atom in the gas. If the free electron has enough kinetic energy, it transfers energy to the atom's outer electron, causing that electron to temporarily jump up to a higher energy level. The collision is 'inelastic' because a loss of energy occurs. • Ultraviolet photons are absorbed by electrons in the atoms of the lamp's interior fluorescent coating, causing a similar energy jump, then drop, with emission of a further photon. The photon that is emitted from this second interaction has a lower energy than the one that caused it. The chemicals that make up the phosphor are chosen so that these emitted photons are at wavelengths visible to the human eye. The difference in energy between the absorbed ultra-violet photon and the emitted visible light photon goes toward heating up the phosphor coating.

5. Why and how different colours?

7. Light from a fluorescent tube lamp reflected by a CD shows the individual bands of color.