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How does a fluorescent lamp change electrical energy into visible light?
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luminescence
Figure 1: Energy levels of a luminescent centre (see text).
A fluorescent lamp converts electrical energy into visible light through a process of gas ionization and fluorescence.
The process functions as follows:
- Ionization: The lamp consists of a glass tube filled with argon and mercury vapor. When electric current flows through the electrodes at the ends of the tube, it ionizes the gas mixture.1
- Ultraviolet Emission: This electrical discharge causes the ionized gas to emit ultraviolet radiation.12
- Visible Light Conversion: The interior of the glass tube is coated with phosphors. These substances absorb the invisible ultraviolet radiation and re-emit the energy as visible light.12
A device called a ballast is essential to this process; it provides the initial high voltage required to ionize the gas and subsequently maintains a stable, lower operating voltage. Unlike incandescent lamps, this method does not rely on the heating of a filament, making it significantly more energy-efficient.1