Light is a complicated thing. It can behave like a wave or a particle.
Most theories in physics talk about it behaving like a wave, when it travels fast splits into the colours of the rainbow and combines again to make white, and creates beams (think of the sunbeams you see through a window). Light bulbs however, whether energy-saving or traditional, rely on light’s particle-behaviour alter-ego.
In 1905 Albert Einstein studied how light can possibly generate energy. This is called the photoelectric effect. He theorized that light can create particle-like entities called photons, which throw off energy. It’s possible to create light-emitting photons under the right conditions, and light bulbs take advantage of this.
The traditional light bulb had been invented a good 28 years before Einstein’s theory, and utilized a variant on it. An atom of a reactive element -tungsten is usually the flavour of choice thanks to its capability to withstand intense heat – will produce light when the electrons within it are excited by an external force. This makes them temporarily speed up and widen their orbit around the nucleus in the middle of an atom. When they’re pulled back to their original orbit, they throw off a photon.
Traditional light bulbs use heat passing across a filament of tungsten to do this. Energy-saving light bulbs use a tube filled with argon gas and mercury vapour. When electrons move from one end to the other, they cause the mercury atoms in the tube to throw off light in the ultraviolet range.
Producing heat requires much more energy than creating enough charge to excite the mercury atoms inside a fluorescent tube. This means that energy-saving light bulbs are exactly that: they require less energy to be pumped into them in order to function. And as they don’t heat up the element that creates the light, it also lasts longer, giving them a longer life span.
Did you know – In a fluorescent tube visible light is produced as a secondary effect of the mercury vapour throwing off photons. The ultraviolet photons react with the phosphor coating inside the tube to produce visible light.