| 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) |
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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, 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) |
| 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) |
| 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) |
| acromial angle | The prominent angle at the junction of the posterior and lateral borders of the acromion. Synonym: angulus acromialis. (05 Mar 2000) |
| acute angle | Any angle less than 90 |
| acute angle closure glaucoma | <ophthalmology> An increase in pressure within the anterior chamber of the eye. There are two forms of glaucoma: acute angle closure and open angle glaucoma. (27 Sep 1997) |
| adjacent angle | An angle with a line in common with another angle. (05 Mar 2000) |
| alpha angle | The angle between the visual and optic axes as they cross at the nodal point of the eye, the angle between the visual line and the major axis of the corneal ellipse. (05 Mar 2000) |
| alveolar angle | The angle between the horizontal plane and a line connecting the base of the nasal spine and the middle point of the projection of the alveolus of the maxilla. (05 Mar 2000) |
| angle | 1. To fish with an angle (fishhook), or with hook and line. 2. <geometry> The figure made by two lines which meet. The difference of direction of two lines. In the lines meet, the point of meeting is the vertex of the angle. 3. A projecting or sharp corner; an angular fragment. "Though but an angle reached him of the stone." (Dryden) Curvilineal angle, one formed by two curved lines. External angles, angles formed by the sides of any right-lined figure, when the sides are produced or lengthened. Internal angles, those which are within any right-lined figure. Mixtilineal angle, one formed by a right line with a curved line. Oblique angle, one acute or obtuse, in opposition to a right angle. Obtuse angle, one greater than a right angle, or more than 90 deg . Rectilineal or Right-lined angle, one formed by two right lines. Right angle, one formed by a right line falling on another perpendicularly, or an angle of 90 deg (measured by a quarter circle). Solid angle, the figure formed by the meeting of three or more plane angles at one point. Spherical angle, one made by the meeting of two arcs of great circles, which mutually cut one another on the surface of a globe or sphere. Visual angle, the angle formed by two rays of light, or two straight lines drawn from the extreme points of an object to the center of the eye. 4. <astronomy> A name given to four of the twelve astrological houses. Origin: F. Angle, L. Angulus angle, corner; akin to uncus hook, Gr. Bent, crooked, angular, a bend or hollow, AS. Angel hook, fish-hook, G. Angel, and F. Anchor. (16 Mar 1998) |