| distance of virtual image | <physics> When a simple lens is used as a magnifier for visual observation the eye becomes part of the optical system. A virtual image can be formulated by construction and its apparent distance will vary with the focus of the eye. This will vary among individuals. In a rather arbitrary but standardised assumption, the normal distance for close observation, or reading has been set at 10 inches (250 mm). The optics for the compound microscope have been designed to furnish parallel light from the eyepiece so that the eyes are relaxed for distant viewing. This makes the virtual image lie at infinity. Tests showed that the average observer accommodates somewhat, placing the virtual image rather variably, often about 20 - 25 feet. (05 Aug 1998) |
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| infinite distance | The limit of distant vision, the rays entering the eyes from an object at that point being practically parallel. Synonym: infinity. (05 Mar 2000) |
| interarch distance | The vertical distance between the maxillary and mandibular arches under conditions of vertical dimensions which must be specified, the vertical distance between maxillary and mandibular ridges. Synonym: interalveolar space, interridge distance. (05 Mar 2000) |
| interocclusal distance | The vertical distance between the opposing occlusal surfaces, assuming rest relation unless otherwise designated. Synonym: interocclusal rest space. Synonym: freeway space. (05 Mar 2000) |
| interpupillary distance | <microscopy, ophthalmology> The distance between the centres of the pupils of the eye. The binocular microscope tube must be adjustable for this distance. (05 Aug 1998) |
| interridge distance | The vertical distance between the maxillary and mandibular arches under conditions of vertical dimensions which must be specified, the vertical distance between maxillary and mandibular ridges. Synonym: interalveolar space, interridge distance. (05 Mar 2000) |
| evolutionary distance | <botany> In phylogenetic trees, the sum of the physical distance on a tree separating organisms, this distance is inversely proportional to evolutionary relatedness. (09 Oct 1997) |
| focal distance | The distance from the centre of a lens to its focus. (05 Mar 2000) |
| large interarch distance | A large distance between the maxillary and mandibular arches; may also imply an excessive vertical dimension. Synonym: open bite. (05 Mar 2000) |