| index of refraction | <physics> For a given wavelength, this is the ratio of the velocity of light in vacuum (c) to the velocity of light in a refractive material (for example, glass, plasma, etc.). (09 Oct 1997) |
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| angle of refraction | <optics> The angle that a ray leaving a refracting medium makes with a line drawn perpendicular to the surface of this medium. (05 Mar 2000) |
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| refraction | <physics> Bending of waves as they pass from a medium having one refractive index to a medium (or region within a medium) having a different refractive index. (09 Oct 1997) |
| refraction, angle of | <microscopy> The acute angle between the normal to a refracting surface at the point of incidence, and the refracted ray. (05 Aug 1998) |
| refraction, ocular | Refraction of light effected by the media of the eye. It also includes the determination of the refractive state and refractive correction. (12 Dec 1998) |
| static refraction | Refraction without accommodation. (05 Mar 2000) |
| double refraction | <microscopy> The refraction of light in two slightly different directions to form two rays or vector components. Each ray is polarized, and their vibration directions are perpendicular to each other. Furthermore, each ray has a different velocity, and therefore a different refractive index. See: birefringence. (05 Aug 1998) |
| dynamic refraction | Refraction of the eye during accommodation. (05 Mar 2000) |
| law of refraction | For two given media, the sine of the angle of incidence bears a constant relation to the sine of the angle of refraction. Synonym: Descartes' law, Snell's law. (05 Mar 2000) |
| absorbancy index | Absorbance (of light) per unit path length (usually the centimeter) and per unit of mass concentration. Compare: molar absorption coefficient. Synonym: absorbancy index, absorptivity, extinction coefficient, specific extinction. (05 Mar 2000) |
| alveolar index | Relation between the basialveolar (basion to alveolar point) and basinasal (basion to nasion) lengths: (basialveolar length × 100)/basinasal length; the result indicates the degree of projection of the maxilla or upper jaw. Synonym: alveolar index. (05 Mar 2000) |
| anaesthetic index | Ratio of the number of units of anaesthetic required for anaesthesia to the number of units of anaesthetic required to produce respiratory or cardiovascular failure. (05 Mar 2000) |
| antitryptic index | An obsolete term for the relative retardation in loss of viscosity of a solution of casein incubated with trypsin, to which a drop of abnormal blood serum (as from a cancerous patient) has been added, compared with that in a similar solution to which normal serum has been added; if the former drips through the tube of the viscosimeter in 100 seconds, and the latter in 104 seconds, the antitryptic index is 4. (05 Mar 2000) |
| Arneth index | An expression based on adding the percentages of polymorphonuclear neutrophils with 1 or 2 lobes in their nuclei, plus one-half the percentage with 3 lobes; the normal value is 60%. See: Arneth formula, Arneth count. (05 Mar 2000) |
| auricular index | Relation of the width to the height of the auricle or pinna: (width of pinna × 100)/length of pinna. (05 Mar 2000) |
| Ayala's index | The cerebrospinal index when 10 ml of cerebrospinal fluid have been removed. Synonym: Ayala's quotient, spinal quotient. (05 Mar 2000) |