How do Light Bulbs Work?

Standard incandescent light bulbs work essentially the same way today that they did at the time of their invention over one hundred years ago. Thomas Edison is generally credited with inventing the light bulb in 1879, though Sir Joseph Swan of England arrived at the idea in 1878. Many inventors of the time were attempting to create a light source to replace candles and oil lamps that were not only dangerous, but dirty. By the turn of the century millions of households had replaced fire and oil with the humble electric light bulb.

At the most basic level, light bulbs work by exciting atoms that release photons of light. Not all photons emit visible light, however. In fact, most of the radiation is emitted as heat rather than visible light. For this reason light bulbs are not very efficient generators of light by today’s standards.

The modern light bulb is a thin, glass chamber filled with inert gases, usually argon. Two metal rods extend upwards into the chamber from contacts at the base of the bulb. A filament of tungsten connects the rods. Tungsten is a key element of light bulbs because it has a very high melting temperature. When electricity is applied to the bulb, it passes through the contacts, rods, and connecting filament, exciting atoms in the tungsten that generate photons.

Excited atoms vibrate. Over time, the tungsten filament weakens as individual atoms vibrate free of the filament. This is an area where one improvement has been made in the way light bulbs work. Bulbs did not contain inert gasses originally, but vacuum which did nothing to prevent the filament from losing atoms. Inert gasses help to extend the life of the filament by providing “bumper” atoms to help knock atoms back into the filament as they escape. The way light bulbs work now is slightly more efficient than the original vacuum design.

Fluorescent lights have a different design that is more efficient than the way light bulbs work. Electricity charges mercury vapor inside the tubular bulb, which in turn excites phosphor atoms that emit white light. Fluorescent lights run cooler, take less energy, and last longer than incandescent light bulbs. However, some people find fluorescent lighting harsh. Flickering fluorescent lighting can also potentially trigger attacks in epileptics.