Black Light & Fluorescence Technical Glossary

Scientific Definitions of Key Concepts in Optics, Photobiology, Spectroscopy & Mineralogy

Terminology Standards

This glossary defines 40+ fundamental scientific terms in accordance with IUPAC, CIE, and ASTM standards.

Actinic Radiation: Electromagnetic radiation capable of producing chemical changes, photochemical reactions, or biological effects, specifically ultraviolet and short-wavelength blue light.
Activator (Mineralogy): A trace foreign element or defect within a mineral crystal lattice (e.g. Mn2+, Eu2+, UO2^2+, Cr3+) whose electronic orbital transitions absorb excitation energy and emit fluorescent photons.
ANSI Z87.1: The American National Standard for Occupational and Educational Personal Eye and Face Protection Devices, governing UV absorption requirements for certified safety eyewear.
Auto-fluorescence: The natural, intrinsic emission of fluorescent light from biological tissues, collagen, elastin, nicotinamide adenine dinucleotide (NADH), and flavins without the addition of exogenous fluorescent stains.
Bandpass Filter: An optical device that passes frequencies within a certain range while rejecting (attenuating) frequencies outside that range, such as a ZWB2 filter passing 320-390nm UV-A and blocking visible light.
Beta-Carboline: A heterocyclic alkaloid organic compound found in the epicuticular hyaline layer of scorpions responsible for their intense cyan-green fluorescence under UV-A irradiation.
Blacklight Blue (BLB): A fluorescent discharge lamp constructed with an integral Wood's filter glass envelope that absorbs visible radiation while transmitting longwave UV-A.
Chemiluminescence: The emission of light resulting directly from a chemical reaction without the absorption of external photons or heat (e.g., the Luminol reaction with blood).
Coproporphyrin III: An endogenous porphyrin metabolite synthesized by Corynebacterium minutissimum that produces pathognomonic coral-red fluorescence under Wood's lamp examination.
Erythema: Reddening of the skin caused by capillary congestion resulting from acute photochemical damage, primarily induced by UV-B and shortwave UV radiation rather than UV-A.
Excitation Spectrum: The relative efficiency of different wavelengths of incident light in exciting fluorescence or phosphorescence in a specific fluorophore.
Fluorophore: A functional chemical group or molecule containing conjugated pi-electron systems capable of absorbing incident photons of specific wavelengths and re-emitting them at longer wavelengths.
Fluorescence: A form of photoluminescence where photon absorption excites singlet-state electrons that decay radiatively to the ground state within nanoseconds (10^-9 to 10^-7 s), halting immediately when excitation ceases.
Fluorescent Penetrant Inspection (FPI): A non-destructive testing (NDT) method utilizing capillary action to draw fluorescent dye into micro-defects, inspected under high-intensity 365 nm UV-A per ASTM E1417.
InGaN (Indium Gallium Nitride): A direct bandgap semiconductor alloy whose tunable bandgap enables solid-state light-emitting diodes (LEDs) to emit narrow-band radiation in the near-UV and violet spectrum (365 nm to 405 nm).
Intersystem Crossing: An isoenergetic, non-radiative quantum mechanical transition between two electronic states of different spin multiplicity (e.g., singlet excited state S1 to triplet excited state T1), leading to phosphorescence.
Irradiance: The radiant flux received by a surface per unit area, typically measured in microwatts per square centimeter (µW/cm²) or watts per square meter (W/m²).
Jablonski Diagram: An energy diagram illustrating the electronic ground state, singlet excited states, triplet states, and radiative/non-radiative transitions (absorption, fluorescence, phosphorescence, internal conversion).
Microsporum canis: A zoophilic dermatophyte fungus causing tinea capitis and tinea corporis, producing pteridine metabolites that fluoresce bright apple-green under Wood's lamp.
Nickel Oxide (NiO): The inorganic dopant compound (~9% by weight) introduced into barium-sodium silicate glass to formulate authentic Wood's filter glass.
Non-Destructive Testing (NDT): Techniques for evaluating the properties and integrity of materials, components, or systems without causing permanent physical damage, heavily utilizing 365nm UV-A inspection.
Optical Brightening Agent (OBA): Synthetic chemical additives (fluorescent whitening agents, typically stilbene derivatives) that absorb ultraviolet light and re-emit visible blue light to counteract fiber yellowing.
Phosphorescence: Photoluminescence involving a spin-forbidden radiative decay from a triplet excited state back to a singlet ground state, resulting in lingering emission lasting milliseconds to hours.
Photokeratitis: Painful acute inflammatory ocular damage to corneal epithelial cells caused by exposure to shortwave UV-B and UV-C radiation, colloquially termed welder's flash or snow blindness.
Pityriacitrin: A bis-indole alkaloid fluorophore synthesized by Malassezia yeasts responsible for the characteristic golden-yellow fluorescence of tinea versicolor under Wood's light.
Pyoverdine: A fluorescent peptidic siderophore secreted by Pseudomonas aeruginosa bacteria that fluoresces lime-green under UV-A illumination.
Quenching: Any photophysical or photochemical process that decreases the fluorescence intensity of a given substance, often caused by heavy metal ions (e.g. Fe3+), molecular oxygen, or high fluorophore concentration.
Quinine: A naturally occurring cinchona alkaloid with high fluorescence quantum yield, emitting intense electric cyan-blue light (~450 nm) under longwave ultraviolet radiation.
Radiant Flux: The total radiant energy emitted, reflected, transmitted, or received per unit time, measured in watts (W) or milliwatts (mW).
Robert Williams Wood: American experimental physicist (1868–1955) of Johns Hopkins University who invented Wood's glass in 1903 and pioneered research into ultraviolet spectroscopy and infrared photography.
Stokes Shift: The mathematical difference (in energy, wavenumber, or wavelength units) between the band maxima of the absorption and emission spectra of the same electronic transition.
Tenebrescence (Photochromism): The reversible optical property of certain minerals (such as Hackmanite) to change body color upon exposure to ultraviolet light and fade back upon exposure to visible light.
Uranium Glass (Vaseline Glass): Glass manufactured with 0.1% to 2% uranium dioxide content, exhibiting characteristic vivid apple-green fluorescence under 365 nm and 395 nm excitation due to uranyl ion photophysics.
Uranyl Ion (UO2^2+): A linear dioxouranium cation possessing high fluorescence quantum efficiency, responsible for bright green fluorescence in autunite, hyalite opal, and uranium glass.
Uric Acid Crystals: Inorganic crystalline residues formed during the drying and microbial decomposition of mammalian urine that exhibit dull yellow auto-fluorescence under 365 nm UV-A.
UV-A Radiation: Longwave ultraviolet electromagnetic radiation spanning wavelengths from 315 nm to 400 nm (soft UV), encompassing standard black light emissions.
UV-B Radiation: Midwave ultraviolet electromagnetic radiation spanning wavelengths from 280 nm to 315 nm, responsible for erythema (sunburn) and vitamin D synthesis.
UV-C Radiation: Shortwave ultraviolet electromagnetic radiation spanning wavelengths from 100 nm to 280 nm, possessing germicidal sterilization properties via DNA thymine dimerization.
Wood's Glass: Barium-sodium silicate glass doped with approximately 9% nickel oxide that absorbs visible light (>400 nm) while transmitting a narrow band of ultraviolet-A radiation peaking around 365 nm.
Wood's Lamp: A handheld clinical diagnostic tool consisting of a 365nm UV-A light source integrated with a Wood's filter and magnifier, utilized in dermatology to evaluate pigmentary and infectious skin disorders.
Yooperlite: A colloquial term for syenite rock clasts found along the beaches of Lake Superior in Michigan, characterized by abundant inclusions of fluorescent sodalite that glow vivid fire-orange under 365 nm UV-A.
ZWB2 Filter: An optical bandpass filter glass (equivalent to Schott UG1 and Hoya U-340) used in high-performance 365nm LED flashlights to block secondary visible blue-violet emission and transmit pure UV-A.