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B High Pressure Sodium and Metal Halide lamps near plasma ball

  1. May 20, 2016 #1
    I bought one of these plasma globes, decided to do some experiments with it.
    Since a fluorescent bulb will light up if It's put near the plasma ball, i tried the same with two HID lamps.

    The Metal Halide shows a very pale white arc, which disappears as soon as the plasma ball is turned off...

    But the HPS is different, it emits a purple glow, which stays for several seconds after the plasma ball is shut off.

    1. Why is this?

    2. Also, since the only thing powering those bulbs is the plasma ball, is there any risk of they exploding due to the lack of a ballast?
  2. jcsd
  3. May 25, 2016 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
  4. May 25, 2016 #3
    Sorry if my post was difficult to understand.

    When a sodium lamp (the type used on street lights) is near a plasma globe, it emits a purple glow which continues for several minutes, even after the plasma ball is turned off.

    I think it may be fluorescence, but i'm not sure.
    What causes this glow?

    - I also noticed an orange residue inside the lamp's arc tube.
  5. May 25, 2016 #4


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    It's phosphoresence and normal for Sodium lamps, also visible in fluorescent lamps to a lesser extent. See the video where the Sodium lamp is turned off around 4:25 and fades to a purple afterglow.
  6. May 26, 2016 #5
    Thanks, understood :)
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