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Light from radio waves

  1. Feb 11, 2006 #1
    In a neon light, light is produced when voltage is applied to electrodes that ionize the gas in the tube. Is there any type of gas than can be ionized, and then produce light, by using radio waves as the energy source rather than electricity?
     
  2. jcsd
  3. Feb 11, 2006 #2

    turbo

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    Try Googling "microwave oven" and "neon".
     
  4. Feb 11, 2006 #3
    I don't know what phosphor does in a gaseous state, but a florescent light tube will glow when radiated on.
     
  5. Nov 21, 2006 #4
    I heard an interesting story from a friend once, he said he brought a fluorescent light near a power line and it actually light up somewhat he said. Stupid move, but still cool =p.
     
  6. Nov 21, 2006 #5

    berkeman

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    My roomate my sophomore year in college was a fairly crazy ChemE who also was a DJ for the campus radio station. He and some other crazy DJs used to go up to the roof of the student union where the multi-kW transmit antenna was, and ballast-start flourescent tubes and then take them off the ballast and have fake Star Wars fights with the tubes. The field from the FM transmitter was enough to keep the flourescent tubes glowing. The FM freq was in the 80MHz-ish range, I think, so there's the OP's RF glow.
     
  7. Nov 21, 2006 #6

    Danger

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    Well, you can readily get gas-discharge tubes (not necessarily neon, since they come in different colours), that clip onto the antennae of cell phones and light up from the radio signals when the phone is in operation.
     
  8. Nov 21, 2006 #7

    berkeman

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    No kidding? Do you have a web pointer? I see my family Christmas gifts in this thread.....:blushing:
     
  9. Nov 21, 2006 #8

    Danger

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    You are kidding, right? :confused:
    Just in case not, any cell phone supplier in Canada offers them as an accessory. Also any store such as Radio Shack (now called 'Circuit City' up here) carries them.
    I would have no f'''''in' clue about web pointers. Just talk to a local electronics shop. If worst comes to worst, PM me and I'll set up a cross-border buy for you.
     
  10. Nov 22, 2006 #9

    berkeman

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    No, you're kidding this time. I'm sure about that. My now-teenage kids have every bling there is, especially for their cell phones. If there was an antenna light-up thing, they would have it and I'd be complaining about it. You have to be pulling my leg again!
     
  11. Nov 22, 2006 #10
    This is a common phenomenon of neon tubes exploited by Bristol University in an art installation entitled 'field'
    http://www.phy.bris.ac.uk/ugadmissions/PhysicsArt.html

    As you walk through the tubes your body grounds them out and they extinguish, so the light follows you round.

    If you want to have a play take a neon tube and walk under an electricity pylon pointing the tube towards the conductors. You can map the EField by how the light intensity changes with position and angle.

    I saw an experimental commercial light at a talk for the BRLSI in Bath where a sealed gas tube sat over an RF source. The theory was that the gas tube never runs out, and the RF source can be more robust than neon tube circuits. If you wanted to change the lighting mood you just lifted off one gas tube and dropped over a different one.
     
  12. Nov 22, 2006 #11
    I am amazed that a single post I placed in February has renewed life 9 months later! I am not an engineer. Simply stated, I want to transmit silent radio waves to a sculpture that will have numerous, very small, colored lights that will glow as long as the radio wave transmission remains on. This will take place in a relatively small area, such as a meeting room or a living room/den of a home. The transmitter would be in the same room.
     
  13. Nov 22, 2006 #12

    Danger

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  14. Nov 22, 2006 #13
    Ahh it's this strange colonial counting system - In the home country you posted it on the 2nd of November.

    Remember when I was working out there we took a student out who was 20 and hence couldn't drink. Despite his Birthday being 10th December he celibrated his Alabama Birthday on the 12th of October.

    If you use RF to stimulate a gas discharge you will need to look at the E-Field in the room versus sterilising all your admiring visitors.

    A neat instalation I saw was a set of micro leds embedded into glass connected by transparent conductors. The table thus looked as if it had stars embedded into it. Very impressive and a snip at £20,000.
     
  15. Nov 22, 2006 #14

    berkeman

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    Yeah, you're not going to be using free-space EM radiation to be lighting things in the same space as your visitors. Bad news. But you could use low-level radio signals to tell your independently-powered lights to turn on in some sequence. You can also use radio-linked sensors to sense where your visitors are and control the lights accordingly.
     
  16. Nov 22, 2006 #15

    berkeman

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  17. Nov 22, 2006 #16

    NoTime

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    :rofl: Your kids must be getting old.
    They just arn't keeping up anymore :rofl:
     
  18. Nov 23, 2006 #17
    Thanks, I get the point regarding the radiation. One last thought then: Rather than using radio transmissions, could the same effect be achieved using sound, or ultra sound transmissions?
     
  19. Nov 23, 2006 #18

    Danger

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    For sure. Anything that transmits a signal from one place to another will work. I'd stay away from photodetectors, though, because they're so easily blocked from the IR source.
    One other recommendation is that if you choose ultrasonics, be careful of what frequency is produced. Some have detrimental effects upon people, such as vibrating dental fillings or overloading hearing aids. Something such as the autofocus sensor from a camera would be great.
     
  20. Nov 23, 2006 #19

    berkeman

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    I'd recommend this -- think about how the energy to perform an action is transmitted from one place to another, and what other side-effects that transmission of energy can have. Like, if you use a very focused high power laser beam to transfer energy from one place to another, and nobody can accidentally intercept the beam, then that's good. But you wouldn't splatter a high power RF source all over a room to light stuff for people in the room to see and interact with. Just think about the power transmission mechanism, the power level, and how that power can interact with unintended targets. Makes sense?
     
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