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The Science of Natural Luminescence
The use of heat to produce incandescent light is something for which everyone has a basic understanding. However, other processes exist for producing light without the use of heat: fluorescence, phosphorescence, chemi-luminescence, and bioluminescence. Fluorescence and phosphorescence are forms of photoluminescence which requires an external light or radiation source to produce the glowing effect. Chemi-luminescence and bioluminescence require a chemical reaction in order for the glow to occur.
Fluorescence, a form of photo-luminescence, is defined as a form of electromagnetic radiation emission that is stirred within a substance upon absorption of external radiation and which persists for as long as the incident (external) radiation source continues. Fluorescence is also described as the property of emitting said radiation, as well as the radiation that is emitted by a fluorescent source. Fluorescence change the energy of fluorescent compounds from one color or light wavelength to another. Fluorescence, in nature, allows organisms a way to produce color and light signals in an environment that would otherwise be monochromatic (blue, black).
Fluorescence can be used for a number of applications
- · highlighter pens
- · safety functions like reflective vests for joggers at night and construction workers
- · fluorescent paint for road stripes and reflective surfaces on street signs.
- · fluorescent light bulbs
- · marine buoys
- · a tool in science and medicine, such as the study of genes, study of cell structure, fluorescence microscopy, or as a way to locate mineral resources.
Fluorescent Minerals at the Sterling Hill Mining Museum .
Phosphorescence, another form of photo-luminescence, is similar to fluorescence in that it produces light when exposed to incident (external) radiation. Phosphorescence, however, persists in emitting light after the external light or heat source has been removed, for a period lasting for seconds to hours after the external source has ceased to excite the atoms. Phosphorescence last longer than fluorescence due to molecular structure.
Items that phosphoresce or have phosphorescent paint applied to them include:
- · petroleum jelly
- · glow in the dark paints
- · quinine found in tonic water
- · some detergents
- · clock and watch faces
- · stairwell steps
- · emergency routes and doors
- · glow sticks and glow bracelets
- · glow ink for labeling
- · x-ray contrast medium
The process makes use of chemicals that re-emit light that has been absorbed from the external source. Phosphorescent paints and materials (glow-in-the-dark products) can be recharged by reapplying the external radiation.
Phosphorescent Properties of Porcelain Glazed Bathtub .
Chemi-luminescence produces the glow due to a chemical reaction rather than exposure to outside light or heat source. In this case, two chemicals - when mixed together - react to create a form of light-emitting energy
Examples of chemi-luminescence in action include:
- · fireflies
- · jellyfish
- · glow sticks, the break-and-shake variety (the color is determined by the dye that is added)
- · luminal to make bodily fluids (blood, urine, etc.) glow
- · a catalyst for certain minerals and chemicals (iron, alloys containing copper, certain cleaning fluids like bleach)
Chemoluminescence with luminol .
Bioluminescence is a natural glow produced by living organisms (fireflies, fish, fungi, glow worms, bacteria). In fact, about 90% of the creatures living in deep sea environments produce some form of bioluminescence:
- · to communicate
- · to catch prey
- · to create a camouflage for themselves
- · to scare off predators
- · to attract a mate.
A few species of squid and crustaceans emit clouds of bioluminescent liquid as sort of a smoke-and-mirrors effect in order to elude predators.
Bioluminescence is a form of chemi-luminescence. It depends on a chemical reaction known as adenosine tri-phosphate (ATP) as the energy source that produces the glow. While all bioluminescent animals and organisms have a unique method for producing the glow, the ATP reaction always begins with luciferin, a chemical that reacts to oxygen or minerals, much like luminol.
American Heritage Dictionary.
Web Exhibits. What Is Fluorescence?
Tech FAQs. What Is Phosphorescence?
Science in School. What Is Chemiluminescence?
NOAA. Bioluminescence Is the Production and Emission of Light by a Living Organism.
Haddock, Steven, PhD. Ocean Explorer. Bioluminescence.