How Does a Light Bulb Work?
Inside a light bulb, a glass rod supports a thin, coiled wire called a filament. It is made of tungsten, a special metal that can stand extreme heat. When electricity passes through the tungsten filament, the filament becomes so hot that it glows with a bright light.
Before the bulb and its contents are sealed up tight all the air is pumped out, and a special non-burning gas is put in. This is done because the hot filament would quickly burn up if exposed to air. The inside of the bulb is given a white coat to make the bulb’s light softer.
Another common type of light is the fluorescent lamp. A fluorescent lamp is a glass tube filled with argon gas and a trough of mercury. When electrical current is passed through the gas the atoms of the gas pick up energy and radiate it in the form of ultra-violet light and some heat. The UV light then strikes the inside of the tube, which is coated with a phosphor. The phosphor glows, giving off the light we see.
Fluorescent lamps don’t require high temperatures to produce light, like incandescent bulbs do. Energy must be used in heating the incandescent bulb, and a large part of that energy is lost as heat, not light. In the fluorescent lamp, a larger portion of the energy is radiated as light.