Are there simple ways to test whether a light is likely short wave / UV-C, or at least whether it is probably a fake?

Real Example: 2 lights are allegedly germicidal and supposedly emit germicidal 254nm radiation.

  • Light 1 darkens transition glasses and emits the smell of chlorine / ozone.
  • Light 2 does neither but appears much brighter than Light 1.

Does the ozone smell of Light 1 entail that it at least emits radiation within the UVC band?

Assuming the glasses do darken outdoors and do darken in response to Light 1, given that they do not darken with Light 2, is it safe to conclude Light 2 emits no UV at all?

  • $\begingroup$ I’m voting to close this question because it isn't about biology — please consult the tour, How to Ask, and other help center pages for details. $\endgroup$
    – tyersome
    Aug 30, 2020 at 19:42
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    $\begingroup$ @tyersome will this question be a better fit on one of the other SE sites,if so it should be migrated.i think the question is important to get answered as there is a lot of fake gemicidal lamps on the market and we are in a pandemic at the moment.i do not disagree wit this question beeing a poor fit here on biology but what are the alternatives. $\endgroup$ Aug 31, 2020 at 7:45
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    $\begingroup$ @trondhansen — If I had a good suggestion I would have made it — since this seems to be fundamentally an optics question there might be a place for it in physics. However I'm not familiar with that site, but since this is a "how do I do this at home" question rather than one about fundamentals of science I'm skeptical whether it would be a good fit there. I think there is also a site about DIY/home repairs. Finding the right site is ultimately the responsibility of the poster. Also note that there is no guarantee that there will be a SE site for any particular question! $\endgroup$
    – tyersome
    Sep 3, 2020 at 0:28
  • $\begingroup$ Sometimes Physics SE is very helpful, but not always. I think if you have a little patience and the question is closed and then migrated by a moderator, there's a good chance it will receive an answer, though I don't know if it will be helpful. $\endgroup$
    – uhoh
    Sep 3, 2020 at 12:31
  • $\begingroup$ FYI: a "blacklight" LED will darken transition glasses (Don't ask me how I know!) $\endgroup$ Sep 3, 2020 at 18:33

1 Answer 1


You can do the banana test to identify if it is real or fake.

Get a green banana and cover parts of it with a sticker you now need to expose the banana with the uv light for about one hour,the green banana will get brown/yellow at the exposed part and stay green under the sticker if the uv-c light is genuine..

It is best to do this in a dark room and the banana can not be in a plastic bag or any covering as this might stop the uv-c light.

The uv source needs to be close to the banana for this to work.

If the color of the green banana stay the same after the test your uv-c light is fake.

Never look directly at the uv-c light and do not shine the light on your bare skin.

source https://www.reddit.com/r/BigCliveDotCom/comments/gj9ymb/uvc_the_green_banana_test/

  • 2
    $\begingroup$ Re, "Never look directly at the uv-c light." UV-C exposure will hurt your eyes alright, but it doesn't matter whether you "look at" the light or not. The UV-C rays will never reach your retinas. All of the damage will be superficial. Don't expose any part of your body to UV-C if you can avoid it, and also, don't breathe the ozone. $\endgroup$ Sep 3, 2020 at 18:39

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