Gordaen's Blog

Light… We rely on it and plenty of it because our eyes are terrible. Other mammals would mock us, but their brains are small. It’s a trade off. Over the years, we’ve burned ourselves to find out fire is bright and hot. Eventually, electricity led to the advent of the incandescent bulb, one of the least efficient electronic devices ever made.

Incandescent about 16 lm/W
Incandescent bulbs are still the most common type of household light in most cases. They work by putting current through a filament. Since the filament creates resistance, it begins to heat up. Long story short, the electrons start partying and spitting out photons. Since the heat would burn up the filament if oxygen was available, most bulbs are either vacuums or filled with inert gas. Basically, this kind of light is not efficient because it relies on heat to create the light. If you have ever heated your home with electric heaters, you know that they can become very expensive.

Fluorescent about 50-100 lm/W
Fluorescent lamps are more complex than incandescent bulbs, but they are also quite a bit more efficient. Here is a very simplistic explanation of their operation: electricity excites mercury vapor that is in a gas (such as neon or argon), emitting ultraviolet light. This causes to a phosphor to “fluoresce” (meaning that one spectrum of light is absorbed and another emitted). A phosphor is a substance that glows after being exposed to light. Phosphors are also used in CRT’s, which is what causes screens on old TV’s and computers to glow. Since the process is fairly complex, it’s more efficient (seriously, why do something more complex than incandescent bulbs if it isn’t more efficient?). Well, okay, the process is more efficient largely because so little heat is produced.

Halogen about 16 lm/W
Halogen bulbs are actually very similar to incandescent bulbs. Instead of glass, they enclose the filament in quartz and the “bulb” is very close to the filament. The fixture is filled with a halogen gas. The vapor from the filament combines with the halogen and is redeposited on the filament, keeping it from burning out quickly. This also allows the filament to be much hotter, giving off more light. Since it is still essentially using the same process as the incandescent bulb, it becomes very hot.

LED (Light Emitting Diode) about 35 lm/W (for the most common ones)
It’s interesting to see commercials for flashlights that use LED’s and make them sound like the “new cool thing.” LED’s have been around for about fifty years. Even after electronics courses, it’s hard to explain LED’s in a “simple” manner. A diode is created (doped) with specific “impurities” that create a cathode (n) and an anode (p). As electrons cross the diode, they release energy as photons. The difference in the materials that form the diode influence the type of light that it emits. The first LED’s that emitted white light (and were thus useful for more than just saying: “hey I’m on” or “look here, something is broken”) were made in the 1990’s.

Those aren’t the only types of lights, but I’m sure most people didn’t bother to read this far anyway. Congrats on being one of the few!