2006-10-17 13:13:35 · 9 answers · asked by Anonymous in Science & Mathematics ➔ Physics
If you mean the red/yellow/green traffic lights, most have been replaced by collections of Light Emitting Diodes that don't contain gas.
Street Lamps usually contain sodium gas at high pressures. As a side note, high-pressure sodium emits light at a wider frequency range and is consequently whiter then the older low-pressure sodium lamps that are yellower in appearance. Astronomers have tried unsuccessfully to lobby against their installation as the whiter light is harder to filter from astronomical observations, a situation known as light-pollution.
2006-10-17 13:27:43 · answer #1 · answered by Al 3 · 1⤊ 0⤋
Conventional red-yellow-green traffic signals contain either incandescent lamps (usually filled with argon, at low pressure, which does nothing other than to slow evaporation of tungsten from the filaments), or light-emitting diodes, which are solid and contain no gas. Some Walk - Don't Walk signs are filled with neon, which is illuminated by passing a high voltage through it.
2006-10-17 13:17:44 · answer #2 · answered by Anonymous · 1⤊ 0⤋
according to the website: http://www.edinformatics.com/inventions_inventors/traffic_lights.htm
In the mid 1990s, cost-effective traffic light lamps using light emitting diodes (LEDs) were developed; prior to this date traffic lights were designed using incandescent halogen light bulbs. Unlike the incandescent-based lamps, which use a single large bulb, the LED-based lamps consist of an array of LED elements, arranged in various patterns. When viewed from a distance, the array appears as a continuous light source (unless closely examined).
2006-10-17 13:24:51 · answer #3 · answered by winorlose9 2 · 1⤊ 0⤋
there is no "gas" in ordinary old style traffic lights. however, they have started to retrofit some older traffic lights with a xenon strobe running across the red lens that flashes when the light is red.
2006-10-17 13:16:52 · answer #4 · answered by Anonymous · 0⤊ 2⤋
in the '90s we started using some of the LED signals since they were less hot and are brighter than the old halogen and incandesant lights.
-eagle
2006-10-17 13:19:28 · answer #5 · answered by eaglemyrick 4 · 0⤊ 0⤋
The ones that aren't L.E.D.'s are filled with argon.
2006-10-17 13:16:18 · answer #6 · answered by spackler 6 · 1⤊ 0⤋
there is a web site called
howstuffworks.com
you can learn about anything!
I love this site and so does my Grandson!
2006-10-17 13:16:42 · answer #7 · answered by itsybitsykity 3 · 0⤊ 1⤋
Methane. Usually leads to soiled pants if it doesn't turn green soon enough.
2006-10-17 13:15:58 · answer #8 · answered by Johnny P 4 · 0⤊ 3⤋
argon...possibly.
2006-10-17 13:15:38 · answer #9 · answered by Anonymous · 0⤊ 0⤋