Focal distance or length of a lens or mirror
Focal Fo"cal, a. [Cf. F. focal. See {Focus}.] Belonging to,or concerning, a focus; as, a focal point. [1913 Webster]

{Focal distance, or length, of a lens or mirror} (Opt.), the distance of the focus from the surface of the lens or mirror, or more exactly, in the case of a lens, from its optical center.

{Focal distance of a telescope}, the distance of the image of an object from the object glass. [1913 Webster]


The Collaborative International Dictionary of English. 2000.

Look at other dictionaries:

  • Focal distance of a telescope — Focal Fo cal, a. [Cf. F. focal. See {Focus}.] Belonging to,or concerning, a focus; as, a focal point. [1913 Webster] {Focal distance, or length, of a lens or mirror} (Opt.), the distance of the focus from the surface of the lens or mirror, or… …   The Collaborative International Dictionary of English

  • focal distance — noun the distance from a lens to its focus • Syn: ↑focal length • Hypernyms: ↑distance * * * focal distance noun Focal length • • • Main Entry: ↑focus * * * …   Useful english dictionary

  • Focal — Fo cal, a. [Cf. F. focal. See {Focus}.] Belonging to,or concerning, a focus; as, a focal point. [1913 Webster] {Focal distance, or length, of a lens or mirror} (Opt.), the distance of the focus from the surface of the lens or mirror, or more… …   The Collaborative International Dictionary of English

  • focal length — leŋ(k)th n the distance of a focus from the surface of a lens or concave mirror symbol f * * * the distance between a lens and an object from which all rays of light are brought to a focus. Symbol f …   Medical dictionary

  • focal length — n. the distance from the optical center of a lens or curved mirror to the point where light rays from a very distant object converge: also focal distance …   English World dictionary

  • focal length — noun count SCIENCE the distance from the center of a LENS or mirror to its focal point …   Usage of the words and phrases in modern English

  • Focal length — The focal length of an optical system is a measure of how strongly it converges (focuses) or diverges (diffuses) light. A system with a shorter focal length has greater optical power than one with a long focal length. Thin lens approximation For… …   Wikipedia

  • Lens (optics) — For other uses, see Lens. A lens. Lenses can be used to focus light. A lens is an optical device with perfect or approximate axial symmetry which tra …   Wikipedia

  • focal length — Optics. 1. the distance from a focal point of a lens or mirror to the corresponding principal plane. Symbol: f 2. the distance between an object lens and its corresponding focal plane in a telescope. Also called focal distance. [1745 55] * * * …   Universalium

  • focal length — UK / US noun [countable] Word forms focal length : singular focal length plural focal lengths physics the distance from the centre of a lens or mirror to its focal point …   English dictionary

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