Jeopardy! category: AN ECO-CATEGORY (10-04-2014)
$1000 clue: More efficient than filament bulbs, this light source gets its name from its twin terminal structure
The gist: Not the curvy ones! Those are CFLs, compact fluorescent lamps, which get their name simply because they’re smaller than the big tubes that most people think of when they hear “fluorescent bulb.” LED (or light emitting diode) bulbs, on the other hand, make light using diodes, from the Greek for “two paths” (“triode” would be the Greek equivalent of “trivia“). A diode is an electronic component that, using a semiconducting material, allows the flow of electricity in one direction while restricting it in the other (i.e. creating a direct as opposed to alternating current). It does this by having two distinct parts, one positively charged and the other negative. The flow of electricity through the diode causes electrons from the negative bit to jump into the positive bit, where they occupy a lower energy level than they had before – which means that they have lost energy. That energy winds up being emitted as photons. If the materials in the semiconductor use in the diode have the right arrangement of electrons, the photons emitted will have a frequency that’s visible to human eyes, and you can use it to read by (and in LED bulbs, the construction of the bulb itself is such that most of the light is transmitted out instead of just being absorbed by the semiconductor). On other hand, if the frequency of the photons is too short (infrared) or too long (ultraviolet), they can be useful for other things, like letting a remote control talk to a TV without sending light bouncing off the screen and into your eyes.
In terms of eco-friendliness (and this week’s category), LED bulbs have a few advantages. As opposed to traditional incandescent lightbulbs, LEDs don’t have a filament that degrades the more time it spends heated up, and so they last much longer. As opposed to fluorescents, which also lack filaments, LEDs don’t contain toxic mercury, which makes disposing of fluorescent bulbs quite tricky. The biggest advantage of LEDs, though, is their energy efficiency. According to Wikipedia’s handy table, LEDs use about a sixth of the wattage of incandescents and two-thirds that of CFLs. Unfortunately, LEDs remain much more expensive than other options, but rapid progress is making them better and cheaper.
The clue: There’s a reason I opened this post with the distinction between LEDs and CFLs – the latter have been in the news, and I suspect that they what comes to mind first when most people think of efficient eco-friendly bulbs. None of the contestants took the bait, though.
In Jeopardy!: While I can’t search “LED” very easily, “light emitting diodes” brings up eight clues in the J!Archive. Six of them give the acronym and look for the long version. Of the other two, one is this clue, and the second asks about the infrared light that comes out of the diode in your remote control. Many of the clues also make reference to energy efficiency, but don’t let yourself get confused with CFLs.