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Is the strength of blacklight Flourescence proportionate to the strength of the source, or is there a threshold? Answered

Say I have a black light hooked up to a dimmer switch and a material that fluoresces under black light. As I gradually increase the 'brightness' of the black light, can I expect the fluorescent material to fluoresce gradually brighter, or is there a definite 'threshold' below which there is no fluorescence?

Will the same hold true for IR-fluorescent materials and IR sources?

Thanks in advance!

3 Replies

orksecurity (author)2009-11-14

Going the other direction (increasing the excitation) does hit a limit eventually, when you've run out of valance electrons to pump to the excited state. And I would presume there's an asymptotic approach to that limit.

Odds of your ever hitting the limit with normal UV sources are pretty darned low, though.

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lemonie (author)2009-11-14

UV tubes work on plasma-discharge, like CFL and other fluorescent tubes. They don't take well to dimmer circuits because you need so much power to ignite the plasma, and they're current-controlled.

Otherwise you're correct in your expectations. You might think about controlling the amount UV light with an aperture, e.g. a slit which you can adjust the width of?


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killerjackalope (author)2009-11-14

Well, there's a threshold for where your vision won't pick up any fluorescence but it happens regardless, until there's no light of that wavelength hitting the material...

I would give you a rundown of the principles behind it but I can't remember the way to describe it very well.

The easiest way to experiment is with a blacklight and some fluorescent materials, move them further away and get and idea, if you've got a camera with a reasonably sensitive sensor you can observe it beyond your vision, though it might involve some slow shutter speeds to really test it.

I have two blacklights somewhere in the house if you're really interested though I don't like them very much, my eyes glow and it makes for a headache inducing haze... Sadly they don't fluoresce in a creepy evil way...

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