Let's take a closer look at the mechanism by which fluorescent light emits ultraviolet rays.

Electrons emitted from the electrode collide with the mercury atoms comprising the vapor inside the glass tube. This causes the mercury atoms to enter an excited state, in which the electrons on the outermost orbit of the atoms and molecules obtain energy, causing them to jump to a higher orbit. Excited mercury atoms constantly try to return to their former low energy state (ground state), because they are so unstable. When this happens, the energy difference between two orbital levels is released as light in the form of ultraviolet waves. However, since ultraviolet rays are not visible to the human eyes, the inside of the glass tube is coated with a fluorescent material that converts ultraviolet rays to visible light. It is this coating that causes fluorescent lamps to glow white.

Fluorescent lamps are not always straight tubes. They come in other forms such as rings and bulbs. Some types of fluorescent lamps have undergone ingenious modifications, such as lamps using a metal line on the outer surface of the tube (rapid start type), eliminating the need for a gas discharge lamp inside.