# How do Black-Lights work?
**URL:** https://boards.straightdope.com/t/how-do-black-lights-work/92425
**Category:** Factual Questions
**Created:** [November 9, 2001, 2:15pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425 "2001-11-09T14:15:56Z")
**Posts on this page:** 13
**Page:** 1
### Author:  [@MarkyDeSade](https://boards.straightdope.com/u/MarkyDeSade)
#### Post date: [November 9, 2001, 2:15pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/1 "2001-11-09T14:15:56Z")
I know this sounds silly, but I really need to know! It’s been bugging me for weeks. What frequencies are being emitted? Are they part of the normal spectrum? Are they dangerous!?!! HELP!!!
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### Author:  [@SpaceDog](https://boards.straightdope.com/u/SpaceDog)
#### Post date: [November 9, 2001, 2:28pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/2 "2001-11-09T14:28:19Z")
Here, in the UK, they’re generally called Ultra-violet lights. [This](http://www.blacklite.com/Technical/black_lights_ultraviolet_lights.htm) page gives most of the answers you’re seeking.
As for dangerous, I’d assume not, as it says the range is ‘just outside’ the visible spectrum. So I’d assume that they’re a fair amount of these wavelengths around.
Somebody more informed will be along in a second in case I’m sadly mistaken.
SpaceDog
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### Author:  [@Nukeman](https://boards.straightdope.com/u/Nukeman)
#### Post date: [November 9, 2001, 2:36pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/3 "2001-11-09T14:36:59Z")
UV can be dangerous, though generally in small doses only for the eyesight (thats why sunglasses protect against 'UVA/UVB rays). In larger doses UV can cause skin cancer (as it is ionising radiation). However, small doses will not do much harm, especially since UV is a component of sunlight, and it is UV that gives you a tan
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### Author:  [@vanilla](https://boards.straightdope.com/u/vanilla)
#### Post date: [November 9, 2001, 2:37pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/4 "2001-11-09T14:37:35Z")
I LOVE them.
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### Author:  [@MarkyDeSade](https://boards.straightdope.com/u/MarkyDeSade)
#### Post date: [November 9, 2001, 2:44pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/5 "2001-11-09T14:44:54Z")
Thanks for the link. Good info, but what’s “Near Ultraviolet?” On my handy color spectrum chart, there is a transition from violet to ultraviolet, with no mention of “near” ultraviolet. In my opinion, it either is or isn’t. In any case, ultraviolet rays cause cancer, tanning, etc…, right? Where’s my tan?
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### Author:  [@SCSimmons](https://boards.straightdope.com/u/SCSimmons)
#### Post date: [November 9, 2001, 2:48pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/6 "2001-11-09T14:48:22Z")
> [@](#):
>
> \*Originally posted by MarkyDeSade \*
> \*\*Thanks for the link. Good info, but what’s “Near Ultraviolet?” On my handy color spectrum chart, there is a transition from violet to ultraviolet, with no mention of “near” ultraviolet. In my opinion, it either is or isn’t. In any case, ultraviolet rays cause cancer, tanning, etc…, right? Where’s my tan? \*\*
The ‘near ultraviolet’ refers to ultraviolet that is near the visible spectrum. The frequency and intensity of your typical blacklights is not going to tan you, blind you, or give you cancer. You need to go to a tanning booth for these. Unfortunately, you can’t get the first without the other two …
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### Author:  [@handy](https://boards.straightdope.com/u/handy)
#### Post date: [November 9, 2001, 3:06pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/7 "2001-11-09T15:06:15Z")
sure thing: [howthingswork.com](http://howthingswork.com)
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### Author:  [@Squink](https://boards.straightdope.com/u/Squink)
#### Post date: [November 9, 2001, 5:33pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/8 "2001-11-09T17:33:01Z")
\*\*Various terms used to describe the wavelength of Ultraviolet light: \*\*
Extreme 70-90 nm
Far 90-200 nm
Near 200-340 nm
Ozone-producing 180-220 nm
Bactericidal (germicidal) 220-300 nm
Erythemal (skin reddening) 280-320 nm
Black light 320-400 nm
UV-A (315-400 nm)
UV-B (280-315 nm)
UV-C (100-280 nm).
[A,B,C,Black etc.](http://www.fastlamps.com/pages/glossary.asp#71)
Extreme, Far and Near UV
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### Author:  [@Running\_with\_Scissors](https://boards.straightdope.com/u/Running_with_Scissors)
#### Post date: [November 9, 2001, 6:53pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/9 "2001-11-09T18:53:52Z")
I believe [this](http://www.howstuffworks.com/question59.htm) is what **Handy** was referring to.
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### Author:  [@mmmiiikkkeee](https://boards.straightdope.com/u/mmmiiikkkeee)
#### Post date: [November 10, 2001, 3:48am UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/10 "2001-11-10T03:48:14Z")
I know there are some UV light sources that are used for disinfection of various things, and these are dangerous (look at them and they can blind you). I’m assuming that the radiation these things put out are UVB or C rays, whereas blacklights put out UVA. No wonder people can still see after they leave the bar!!
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### Author:  [@scr4](https://boards.straightdope.com/u/scr4)
#### Post date: [November 10, 2001, 3:53am UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/11 "2001-11-10T03:53:36Z")
> [@](#):
>
> \*Originally posted by Nukeman \*
> \*\*However, small doses will not do much harm, especially since UV is a component of sunlight, and it is UV that gives you a tan \*\*
But when you are in full sunlight, the pupils contract and protect your eyes. If you take just the UV component of it and shine it into your eyes it would do more damage. I can’t give quantitative answers though, sorry.
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### Author:  [@MarkyDeSade](https://boards.straightdope.com/u/MarkyDeSade)
#### Post date: [November 10, 2001, 8:42am UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/12 "2001-11-10T08:42:31Z")
Thanks. You all have been more than helpful. Now maybe I’ll be less confused the next time I go to a rave. 🙂
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### Author:  [@handy](https://boards.straightdope.com/u/handy)
#### Post date: [November 10, 2001, 10:54pm UTC](https://boards.straightdope.com/t/how-do-black-lights-work/92425/13 "2001-11-10T22:54:08Z")
frogstein, [howthingswork.com](http://howthingswork.com) directs to [howstuffworks.com](http://howstuffworks.com) I never thought of that.