If you have been using rapid antigen tests a lot in the past few months, you may now have several UV flashlights in your possession.
Don’t throw them away: Torches, which come with some (but not all) RATs, could lead you to an important scientific discovery. Or at least something fun to do for an hour while you’re isolated. There are at least half a dozen things in your home that glow or change color under UV light, some quite dramatically.
Why do some things glow under ultraviolet light?
Ultraviolet light is exactly the same as visible light, only it has a little more energy. The photons of ultraviolet light travel at a slightly faster wavelength than those of violet light (hence the term ‘ultraviolet’).
When a photon hits a substance, it can be absorbed and then released again at a different (usually lower) energy level.
What this means in practice is that light of one color can be returned as another color. A substance, like the tiny lines of chemicals on your RAT, can absorb invisible ultraviolet light and then glow green or yellow.
This is called photoluminescence.
What else glows under ultraviolet light?
Many other things have photoluminescent chemicals. Here are some things you could have in your home that glow under UV rays:
- Tonic water: Quinine in tonic water glows blue.
- Honey: The aromatic molecules in honey can glow green.
- Turmeric root: the curcumin in turmeric glows yellow
- Eggs: A compound in eggshells called protoporphyrin IX can glow red
- Rocks, jewels and gemstones: many minerals glow under ultraviolet light
During the initial shutdowns of 2020, some chemists even ran an editorial on Matter on other objects in your kitchen they could shine.
But the list does not end there. Many things have photoluminescent chemicals deliberately added during manufacturing:
- Cash: Notes have photoluminescent details added to prevent fraud
- Cleaning Materials – Detergents often have photoluminescent molecules so they are easy to see.
- Highlighters and Dyes: Fluorescence is a type of photoluminescence, so fluorescent markers and dyes will often glow under ultraviolet light.
- Role: often has fluorescent molecules added to it as well
Did you find something interesting?
Even when they have easy access to ultraviolet light, people often don’t check to see if anything is glowing under it.
It did not occur to any researcher to put a platypus under ultraviolet light until 2020, at which point they were shocked to discover that it glowed green.
That discovery prompted the examination of several other marsupials, showing that wombats and some other Australian mammals also glow.
Surprise fluorescence has also shown up elsewhere, such as pink squirrels in the US.
Just yesterday, an article in Earth and Environment Communications described a fascinating insight into ancient spiders, based on researchers shining an ultraviolet light on some fossils “more or less on a whim.”
So there are a lot of things out there that glow under ultraviolet light. And there are very likely some things we haven’t found yet!
If you discover something unusual that glows under ultraviolet light, Cosmos wants to hear about it. Send a photo of your thing that glows under ultraviolet light to [email protected]and we will send you a copy of Best Australian Science Writing to the winning entry.
Are UV torches dangerous?
We know to avoid ultraviolet light from the sun, due to the risk of skin cancer. Commercial black lights and bug lights are designed to be too weak to cause a hazard, but the UV torches you get on RATs can be stronger.
Check the instructions in your test kit for specific instructions: most will tell you to avoid shining the flashlight directly at your eyes, because there’s a risk UV light could cause damage there, and some will be even stricter. And when in doubt, always avoid bright UV light on your skin.