How do fluorescent lamps use ultraviolet energy from mercury vapour to create visible light?

Fluorescent lamps generate visible light through a process of energy conversion involving mercury vapor and specialized coatings.

When an electric current is applied to the lamp, it creates an electric field that excites the mercury atoms within the tube. As these excited mercury atoms return to their ground state, they emit ultraviolet radiation, most notably at a wavelength of 254 nanometers.12

The interior of the lamp is coated with a phosphor, a solid material designed to absorb this invisible ultraviolet energy. Upon absorbing the ultraviolet radiation, the phosphor undergoes luminescence, re-emitting the energy as visible light. The specific color of the light produced depends on the composition of the phosphor used, such as calcium halophosphate incorporating a heavy-metal activator. This mechanism allows the lamp to efficiently transform high-energy ultraviolet radiation into the visible spectrum required for illumination.342