An incandescent bulb is a type of light source that produces light by dissipating electrical energy as heat in a filament. Incandescent bulbs have been around for more than a century and are still used in many places today. A typical incandescent bulb consists of a glass envelope with either a tungsten or halogen filament inside. The filament is connected to an electric current which causes it to heat up, emitting visible light and some infrared radiation. The brightness of the bulb is adjustable depending on the amount of current supplied to the filament.