Glow in the Dark: The Essence of Fluorescence 

Bright paints, luminous deep-sea fish, glowing gemstones, and your watch face. All these things have one thing in common; they’re fluorescent. What’s behind this enchanting phenomenon?

The essence of fluorescence

Think about charging your smartphone for a moment. You plug your charger into the wall, the cable draws electricity from the socket and delivers it to your phone. Your phone is equipped with a battery that is able to accept and store the electricity until it has a full charge. Once you’ve unplugged your phone, there is a gradual release of the stored energy in the reservoir until it runs out—probably after one too many Snapchats.

That is essentially the same principle behind the concept of fluorescence, but on a much smaller and faster scale. When some materials are exposed to a certain range of light or other types of radiation (not necessarily harmful), the electrons at the molecular level “charge up” instantaneously. Once the source of energy is removed (e.g., the light is turned off), the energy is released in the form of visible light.

Voila! It’s glowing right before your eyes.

Why do some things under a black light look so groovy?

Let’s take the concept of fluorescence one step further with a black light as the example. You may already be aware that black lights emit ultraviolet (UV) rays. What you may not know is that these rays are invisible to the human eye and give off more energy than regular light bulbs.

While we’re blind to the black light charging up the electrons on your white T-shirt, the light that is released is at a slightly lower energy level and in the visible range that we see. The results are the dramatic, highlighter orange, green, and blue colors your sneakers give off while you’re playing laser tag or hitting the dance floor at the disco.

Wild (and not so wild) applications of fluorescence

It’s not all fun and games. Fluorescence can also be practical and useful in everyday society. Most credit cards, banknotes, and postal stamps have fluorescent security features. Some chemical compounds cause fingerprints to fluoresce, allowing forensic specialists to gather more information on crime scenes. Even some medical dyes are designed to fluoresce, providing doctors with many medical uses.

Of course, we cannot leave out glow-in-the-dark coatings and materials. While this is a form of phosphorescence, light emitted by a substance without combustion or perceptible heat, the principle is similar and just as useful. To this day, many of the dials and scales of aviation and navigational instruments are coated in glow-in-the-dark substances for safety purposes.

Wait, spiders can also glow?

Like accents on a classic car’s paint job, arachnids are quite commonly decorated with fluorescent bands, strips, and patches that give them some flair in the presence of UV light. That’s right, if you shine a black light over a wide variety of spider species, you’re likely to see them in a completely different light—literally. As per many things in the animal kingdom, biologists, zoologists, and entomologists all suspect that florescence has evolved over time because of mating behaviors.

Scorpions, also in the arachnid family, very famously glow in the presence of UV light. Many a Texan has been known to go looking for the fascinating creatures at night with UV flashlights.

Pretty spectacular, right?

We hope you've enjoyed learning more about fluorescence and your amazing vision.     

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