Dispersion

Related terms

ASTM E1967

The ASTM International standard for forensic glass RI measurement; specifies three acceptable methods (automated, semi-automated, manual), minimum precision of ±0.0001 RI units,...

Bayesian Likelihood Ratio

A statistical framework for expressing the evidential value of a comparison: the ratio of the probability of the observed RI similarity given...

Becke Line

The bright optical halo at the edge of a solid fragment immersed in a liquid, visible under the microscope; moves toward the...

Cauchy Equation

The empirical equation n(λ) = A + B/λ² + C/λ⁴ that describes the wavelength dependence (dispersion) of a material's refractive index; used...

ENFSI ENG3-2013

The ENFSI Glass Expert Working Group guideline for glass comparison casework; specifies the examination sequence, within-source variation requirements, statistical comparison framework, and...

GRIM-3

Glass Refractive Index Measurement, third-generation instrument by Foster + Freeman (UK); an automated phase-contrast hot-stage system that identifies the RI match point...

Immersion Method

The forensic technique of matching a glass fragment's RI to that of a reference oil by adjusting temperature; the fragment becomes invisible...

Locke 1985 Protocol

The calibrated immersion-oil series and operational procedure for forensic glass RI measurement described by Locke and Underhill (1985); specifies the oil series,...

Mettler FP-90

A general-purpose laboratory hot stage widely used in forensic glass RI measurement to provide ±0.1 °C temperature control for the manual Becke-line...

Phase-Contrast Microscopy

An optical technique that converts phase differences (RI differences at an interface) into intensity differences visible in the image; exploited by the...

Refractive Index (RI)

A physical property of glass measuring how much light bends as it passes through. RI is the primary discriminating characteristic used in...

Explained in

• Refractive Index: Becke Line, GRIM and Mettler Hot StageThe variation of refractive index with wavelength; all glasses and immersion oils show dispersion, which is why RI must be specified at a defined wavelength (c...