| plus lens | A converging lens. Synonym: plus lens. (05 Mar 2000) |
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| plus | 1. <mathematics> More, required to be added; positive, as distinguished from negative; opposed to minus. 2. Hence, in a literary sense, additional; real; actual. "Success goes invariably with a certain plus or positive power." (Emerson) 3. <mathematics> Plus sign, the sign (+) which denotes addition, or a positive quantity. Origin: L, more; akin to Gr, and cf. Piu, Pleonasm. (11 Mar 1998) |
| plus strand | See: replicative form. (05 Mar 2000) |
| fluorescence plus Giemsa stain | <technique> A stain used to demonstrate sister chromatid exchange; cells are grown in 5-bromodeoxyuridine, followed by chromosome preparation, staining in Hoechst 33258, exposure to light, and staining in Giemsa; chromosomes exhibit a "harlequin" appearance. (05 Mar 2000) |
| achromatic lens | A compound lens made of two or more lens's having different indices of refraction, so correlated as to minimise chromatic aberration. (05 Mar 2000) |
| acoustic lens | In ultrasonography, a lens used to focus or diverge a sound beam; may be simulated by electronic manipulation of signals. (05 Mar 2000) |
| anterior pole of lens | The central point on the anterior surface of the lens of the eye. Synonym: polus anterior lentis. (05 Mar 2000) |
| anterior surface of lens | The anterior surface of the lens of the eye. Synonym: facies anterior lentis. (05 Mar 2000) |
| aplanatic lens | A lens designed to correct spherical aberration and coma (q.v.). Synonym: periscopic meniscus. (05 Mar 2000) |
| apochromatic lens | A compound lens designed to correct both spherical and chromatic aberrations. (05 Mar 2000) |
| asphenc lens | <physics> A lens made aplanatic by grinding the outer zones to a greater radius than the inner zones. Aplanatic condensers can be made in this way. A simple aspheric lens is widely used as a lamp condenser because of its efficiency in converging light rays to one focal plane. (05 Aug 1998) |
| aspheric lens | A lens with a paraboloidal surface that eliminates spherical aberration. (05 Mar 2000) |
| astigmatic lens | A lens in which one of the surfaces is curved in one meridian and less curved in the opposite meridian; e.g., a teaspoon or a football. Synonym: astigmatic lens. (05 Mar 2000) |
| axis of lens | A line connecting the anterior and posterior poles of the lens of the eye. Synonym: axis lentis. (05 Mar 2000) |
| back lens | <physics> In any compound lens (a lens system composed of more than one lens element), the last lens through which the light passes is called the back lens. It may be a single simple lens, a doublet, or triplet. See: front lens (05 Aug 1998) |