Electromagnetic Spectrum
Definition
The full range of electromagnetic radiation by wavelength, from gamma rays (shortest) to radio waves (longest). Forensic devices use UV, visible, IR and X-ray bands; rarely neutron.
- Range
- Gamma rays to radio waves
- Forensic bands
- UV, visible, IR, X-ray
- Rarely used band
- Neutron
- Ordering
- By wavelength
Common questions
Why do forensic devices concentrate on the UV, IR, and X-ray bands rather than the full spectrum?+
These bands interact usefully with common evidence: UV and IR reveal latent marks, alterations, and biological fluorescence invisible to the eye, while X-ray penetrates opaque objects for imaging, whereas bands like gamma or radio have little practical application in routine casework.
What determines which part of the spectrum a given crime detection device uses?+
The choice depends on how the target material interacts with that wavelength range, for example ink and paper often show differential absorption or fluorescence in IR or UV that is invisible under normal light, so the device band is selected to exploit that specific material property.
Related terms
- Alternate Light Source (ALS)
- A device emitting light at selected wavelengths (typically 415 to 535 nm) used to detect biological fluids that fluoresce or absorb light...
- Detective Dye
- A powder (typically anthracene or phenolphthalein-based) applied to banknotes or surfaces. Transfers to the suspect's hands on contact; anthracene fluoresces under UV...
- Fluorescence
- Light emission following absorption of light at a shorter (higher-energy) wavelength. Fluorescein absorbs blue-green excitation light and emits yellow-green light. The emitted...
- IR Reflectance
- Imaging under near-infrared illumination (715-1000 nm) to differentiate inks by their IR absorption: carbon-based inks remain dark, many synthetic dye inks become...
- Neutron Radiography
- Imaging technique using a thermal-neutron beam that penetrates dense metal and resolves light-element components like explosives, plastics and adhesives. Rare; used for...