Regis: Hi, Barbara. Are you using the new light bulbs? Fluorescent tubes have been shrunk into white spiral bulbs called compact fluorescent lights (CFLs). They use less energy!
Barbara: Well, I just bought a fuel-efficient car. Should I change my light bulbs also? Can I make a difference by changing a single light bulb?
Regis: Actually, it is estimated that exchanging one incandescent bulb for a CFL will save you $105 over the lifetime of the CFL because they last 10 times as long!
Barbara: Ordinary light bulbs, developed by Thomas Edison, have been used for more than 100 years. In these light bulb, electrical energy simply runs through a tungsten filament where it is converted to heat energy. As the filament heats to 2,000 oC, the tungsten atoms gradually vaporize, causing the filament to break and the bulb to “burn out.” Also, these light bulbs are cheap.
Regis: CFLs produce light by a completely different process. Most of the electrical energy is transformed into light rather than heat energy. CFLs contain argon, a nonreactive noble gas, and a drop of mercury (Hg). When you turn on the electricity, electrons excite the Hg atoms. As these atoms return to lower energy states, they release the absorbed energy as ultraviolet (UV) light. CFLs are coated with phosphor, a compound that absorbs UV light and then emits light of a longer wavelength—in this case, in the visible light range.