Ultraviolet Light is electromagnetic radiation that occurs in the part of the light spectrum between X-rays and Visible light, at approximately 180 nanometers to 400 nanometers. It differs from light only that its wavelengths are too short to be seen by the human eye.

  • UV-A, long wave radiation, is 315 nanometers and above.
  • UV-B, midrange radiation, is 280 nanometers to 315 nanometers.
  • UV-C, short wave radiation, is 280 nanometers and below.

The phenomenon known as fluorescence occurs at the subatomic level by the process called electron excitation. Electrons are subatomic particles that orbit the nucleus of an atom at specific distance known as electron shells. The shells are arranged in layers around the nucleus, the exact number of electrons and their shells depending on the type of the atom (element). The electrons contained in the shell nearest the nucleus carry less energy than the electrons in the outer shell.

When certain atoms are exposed to ultraviolet light, a photon (particle of light energy) of UV will cause an electron residing in a lower-energy inner electron shell to be temporarily boosted to a higher-energy outer shell. In this condition, the electron is said to be excited. It will then drop back to its original inner electron shell, releasing its extra energy in the form of a photon of visible light. This visible light is the florescent color that our eyes perceive. The exact color depends on the wavelength of the visible light emitted, with the wavelength itself being dependent on the type of atom undergoing the electron excitation.

Fluorescent minerals respond best to either short-wave UV light, or long wave UV light. Some minerals may fluoresce under both wavelengths with the same or similar color, while some may show different colors under each. Most respond best to only one of these two wavelengths.

Scorpions are known to glow when exposed to certain wavelengths of ultraviolet light, due to the presence of fluorescent chemicals in the cuticle. One fluorescent component is now known to be beta-carboline. A hand-held UV lamp has long been a standard tool for nocturnal field surveys of these animals. Fluorescence occurs as a result of sclerotization and increases in intensity with each successive instar.

Exposure to ultra-violet light will cause scorpions to fluoresce and make them easier to spot, even in bright ambient light.

Most lights and LEDs claiming to be ultraviolet are actually 395-400 nanometers which is the very end of the ultraviolet spectrum and the beginning of the visible light spectrum. True longwave UV-A ultraviolet is 365 nm. As you can see in the top photo 365 nm reveals the hidden security markings whereas in the lower picture 395 nm does not.

Caution: Short-Wave (UV-C) and Mid-Range (UV-B) Ultraviolet Rays Are Harmful To Eyes And Skin! Proper Protection Must Be Worn When Operating Lamps Producing Short-Wave and Mid-Range Ultraviolet Light.