UV-C
Definition
Ultraviolet radiation in the 100-280 nm band; the 254 nm germicidal line excites biological-fluid fluorescence in forensic screening.
- Wavelength band
- 100 to 280 nm
- Germicidal line
- 254 nm
- Forensic use
- Excites fluorescence in biological fluid screening
- Position in EM spectrum
- Shortest-wavelength UV subtype (below UV-B and UV-A)
Common questions
Why is 254 nm specifically used for forensic fluid screening?+
This germicidal wavelength efficiently excites the fluorophores in semen, saliva, and other biological fluids, causing them to fluoresce visibly against a dark background, making it a standard alternate light source setting for scene and garment examination.
Is UV-C exposure a safety concern during scene examination?+
Yes, UV-C at 254 nm can burn skin and eyes with prolonged exposure, so examiners use protective eyewear and follow manufacturer exposure limits when operating germicidal-range light sources.
Related terms
- Chromophore
- The molecular subunit responsible for a dye's colour, typically a conjugated double-bond system; chemical erasure destroys the chromophore while leaving the decolourised...
- Ionising Radiation
- Electromagnetic radiation whose photon energy exceeds the ionisation potential of atoms (typically above ~10 eV); includes gamma rays and X-rays. UV below...
- Mid-Infrared (Mid-IR)
- The 2500-25000 nm (400-4000 cm^-1) spectral region where functional-group vibrational absorptions serve as chemical fingerprints; the operating region of FTIR spectroscopy.
- Photon
- A quantum of electromagnetic radiation; a discrete energy packet with energy E = hν where h is Planck's constant and ν is...
- Photon Energy (eV)
- Photon energy expressed in electron volts; UV photons carry 3-12 eV (chemically reactive), visible 1.8-3.1 eV, mid-IR 0.05-0.5 eV (vibrational excitation only).
- Planck-Einstein Equation
- E = hν = hc/λ; relates photon energy to frequency and wavelength. Foundation of all spectral energy calculations.
- Refractive Index
- A physical property of glass (and other transparent materials) that describes how much light bends when passing through it. Forensic glass comparison...
- Soret Band
- The intense porphyrin absorption band of haemoglobin at 415 nm; the spectral basis for bloodstain contrast enhancement.
- UV-a
- The ultraviolet band from 315 to 400 nm; the primary band used for UV-reflectance forensic imaging of bruises, GSR, and bite marks...
- Wave-Particle Duality
- The quantum-mechanical property of electromagnetic radiation: it behaves as a wave (diffraction, interference, polarisation) and as a stream of photons (photoelectric effect,...
- Wavenumber (Cm^-1)
- Reciprocal of wavelength in centimetres, the standard unit for mid-infrared spectra; 1 cm^-1 = 10^7 / λ(nm).