Refractive Index
Definition
A physical property of glass (and other transparent materials) that describes how much light bends when passing through it. Forensic glass comparison measures refractive index to discriminate between glass from different sources.
- Definition
- Ratio of light speed in vacuum to its speed in a medium
- Forensic use
- Discriminates between glass samples from different sources
Common questions
What is refractive index and why does it matter in forensics?+
Refractive index measures how much light bends when it travels through a material compared to vacuum. In forensic glass comparison, this property helps distinguish between glass samples from different sources, making it a key tool for linking evidence.
How does refractive index affect light passing through glass?+
When light enters glass, it slows down and bends at the interface. The refractive index determines both how much it bends and how its wavelength changes inside the material. Different types of glass have different refractive indices, which is why the measurement is forensically useful.
Can refractive index be used to identify unknown glass samples?+
Yes. Because refractive index is a physical property that varies between glass sources, forensic scientists measure it to compare unknown glass fragments against known standards. Matching refractive indices suggests the samples may come from the same source, supporting investigative leads.
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...
- Fire Debris Analysis
- The laboratory examination of material collected from a suspected arson scene to detect and identify accelerants (hydrocarbons from petrol, lighter fluid, or...
- GC-MS
- Gas chromatography-mass spectrometry: a two-stage technique that separates the components of a mixture (GC) and then identifies each component by its molecular...
- 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.
- Serology
- The examination and identification of body fluids at crime scenes, typically blood, semen, saliva, and urine, using chemical tests and immunological methods...
- Soret Band
- The intense porphyrin absorption band of haemoglobin at 415 nm; the spectral basis for bloodstain contrast enhancement.
- STR Profiling
- Short tandem repeat profiling: the same multi-locus PCR-based method used for human identity testing, adapted for target species with species-specific primer sets....
- Touch DNA
- Minute quantities of epithelial cells transferred by skin contact with a surface, without leaving a visible stain. Collected by swabbing contact points...
Explained in these topics
- The Core Lab Sciences: Biology, Chemistry, PhysicsA physical property of glass (and other transparent materials) that describes how much light bends when passing through it. Forensic glass comparison measures...
- Light, Photons and the Forensic EM SpectrumThe ratio of the speed of light in vacuum to its speed in a medium; determines how light bends at interfaces and how wavelength shortens inside a medium.