LIGHTING:INCANDESCENT LIGHTS

INCANDESCENT LIGHTS

Light is a form of energy that can be released by an atom. Photons, the most basic unit of light, are made up of many small particle-like packets that have energy but no mass. Atoms release these photons when excited electrons revert back to their ground state energy. The excitement of these electrons, specifically how much energy is released, determines the wavelength of the emitted light and hence the color of the light. Incan- descent light bulbs are very simple in construction and theory of operation. At the base of the light bulb, there are two metal contacts that connect to the ends of an electrical circuit. The metal contacts are attached to a thin metal filament, usually made of tungsten, and the globe of the bulb is filled with an inert gas to prevent the metal from burning in the presence of oxygen. When the bulb is connected to a power supply, an electric current flows from one contact to the other through the filament. As the electrons move through the filament, they continually bump into the atoms that make up the filament. This constant impact vibrates the atoms and heats the filament atoms to the point at which electrons may temporarily be boosted to a higher energy level. As these electrons return to their ground state, they release energy in the form of photons or light. The metal filament is heated to over 2,200 degrees centigrade, at which point the photons released are at a wave- length that humans can see, otherwise known as visible light. A great deal of energy is given off by incandescent lights that cannot be seen by humans. These wavelengths of infrared light are responsible for the heat that a light bulb emits. Approximately 10 percent of the light an incandescent bulb emits is visible; hence, incandescent bulbs are inefficient, wasting a majority of energy generating heat instead of light.