Luminescence is a process of giving off light without obtaining or generating heat. This can be caused by chemical or biochemical reactions, activity of subatomic particles, radiation or stress on a crystal.
- Chemoluminescence - This process creates light through a chemical reaction. Common applications are glow sticks (cyalume sticks) and the forensic application for locating blood using luminol.
- Crystalloluminescence - Light is made during crystallization and it is theorized that the light comes from small fractures in the crystal.
- Electroluminescence - This occurs when an electromagnetic field is applied to solid or gaseous material. This excites the molecules and the substance glows. LEDs, or light-emitting diodes, are found in flat panel televisions and computer monitors.
- Fluorescence - Fluorescent materials absorb light and then they glow for a certain time. In fluorescent light bulbs an electrical current runs through mercury vapor producing electrons that hit material that is painted on the inside of the bulb.
- Phosphorescence - Phosphorescent materials also glow in the dark; but, their glow lasts longer than fluorescence, making them good for glow in the dark applications. Clocks and watches have phosphorescent paint on them.
- Photoluminescence - This is a process where a substance absorbs photons and then re-emits them. The electromagnetic energy is absorbed at a certain wavelength and is emitted at a different wavelength which is most commonly longer.
- Radioluminescence - Light from this process is made from using radiation or high energy particles to bombard a substance. This is used in medical physics and radar screens.
- Sonoluminescence - This produces light from bubbles that are hitting one another when sound waves passed through the liquid. The sound waves cause bubbles which emit light when popped.
- Thermoluminescence - Light comes from using heat to release of electrons that were trapped in a substance. This process is used in archaeological dating.
- Triboluminescence - In this process, the light coming from the substance is made by friction, like rubbing, crushing, or scratching. The friction pulls apart chemical bonds, thus causing electrical charges.
Bioluminescence is a type of chemoluminescence that is used by living creatures. For example:
- Angler fish - These fish use bioluminescent lures to trap prey. The light comes from bacteria that used bioluminescence to communicate.
- Comb jellies - These glow all over and when a chunk is bitten off by an enemy, the chunk continues to glow, making that creature more visible to predators.
- Deep sea creatures including fish, crustaceans, and squid like the hatchetfish - These creatures can adjust their light output to eliminate their shadow.
- Earthworms - Some secrete a substance that glows that is thought to startle any predators.
- Fireflies - These insects have a chemical reaction in their bodies that converts lucifern into another form and that reaction produces light. They are also called lightning bugs.
- Fungi - There are over 70 species that are bioluminescent. The green glow may attract bugs to help spread spores, may attract the bugs' predators, or may have no particular function.
- Glow worms - These are the larval stage of gnats and these larvae produce sticky lines to catch prey. Then they secrete a glowing substance to attract the prey.
- Loose jaw dragonfish - These fish send out a red light from under their eyes that is essentially night vision.
- Plankton - Also called dinoflagellates, some plankton use their light as a startle mechanism. This may attract larger fish to attack the plankton's predator.
- Sea cucumbers - These have skin that is sticky and glows. It rubs off on their predators, making them more susceptible to other predators.
- Sea worms - Five species of sea worms launch capsules filled with liquid that break open and bioluminescence for a few seconds. This is done to distract predators.
So now you have seen both luminescence and bioluminescence.