Neon lights work by applying high voltage to the electrodes at each end of a sealed glass tube filled with low-pressure neon gas. This ionizes the neon and causes it to glow.
The light of neon gas is created by the constant collision of atoms, ions and electrons. Neon atoms possess 10 electrons: Two orbit the inner energy level, and eight orbit the outer energy level. When an electric current passes through the neon atoms, the eight outer electrons absorb that energy and jump to a higher energy level. In this excited state, the atoms are unstable, and the electrons soon drop back to their original energy levels. The energy that was absorbed is then released in the form of colored light particles called photons.
Neon signs are glass tubes bent into letters or shapes, and the type of gas combined with the color of the glass determines their color. Different gases produce different colors. Neon emits red light, xenon beams like the noon sun, helium glows yellow, krypton washes with white, and argon combined with mercury vapor emits blue. A gas such as blue-glowing argon gas is put in a yellow tube to create green light. When argon is placed in blue glass, dark blue light is created.
Fluorescent lights are similar to neon lights but have an extra step. These lights are filled with low-pressure mercury vapor, which emits ultraviolet light when ionized. The phosphor-coated glass accepts the ultraviolet photons and fluoresces with visible light.