How does a fluorescent light works

A fluorescent light consist of a sealed glass tube filled with an inert gas at a low pressure. Inside the glass tube there is a small amount of mercury. On each end of the tube, there is an electrode. The two electrodes are connected to a high voltage AC electrical circuit. A ballast, which is connected to a standard AC voltage circuit, works as a transformer to increase the voltage across the electrodes.


When the lamp is turned on, the high voltage across the electrodes induces the movement of electrons from one electrode to the other. This flow of electrons vaporizes some of the mercury producing mercury gas. When the electrons collide with the mercury gas molecules, electrons on the mercury gas move towards a higher energy level. When the electrons on the mercury gas molecules return to the lower energy state, they release energy: Photons. This electromagnetic radiation emitted from the mercury is mostly ultraviolet and thus not visible to the human eye. A phosphor power coated onto the glass surface of the glass absorbs the emitted UV radiation and emits visible white light.

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