Focal-length


noun, 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.
noun
1.
the distance from the focal point of a lens or mirror to the reflecting surface of the mirror or the centre point of the lens

focal length n.
The distance from the surface of a lens or mirror to its focal point. Also called focal distance, focus.
focal length
(fō’kəl)
The distance between the optical center of a lens or mirror to its focal point.

The distance between the focal point of a lens (that is, the point at which the lens will focus parallel rays of light) and the lens itself.

Read Also:

  • Focally

    [foh-kuh l] /ˈfoʊ kəl/ adjective 1. of or relating to a . /ˈfəʊkəl/ adjective 1. of or relating to a focus 2. situated at, passing through, or measured from the focus adj. 1690s, from Modern Latin focalis; see focus + -al (1). focal fo·cal (fō’kəl) adj. Of or relating to a focus.

  • Focal necrosis

    focal necrosis n. The occurrence of numerous, small, fairly well circumscribed, foci of necrosis.

  • Focal-plane shutter

    [foh-kuh l pleyn] /ˈfoʊ kəl ˌpleɪn/ noun, Photography. 1. a camera shutter situated directly in front of the film.

  • Focal-plane

    noun, Optics. 1. a plane through a focal point and normal to the axis of a lens, mirror, or other optical system. Compare . 2. the transverse plane in a telescope where the real image of a distant view is in focus. noun 1. the plane that is perpendicular to the axis of a lens […]

  • Focal-point

    noun 1. Also called principal focus. Optics. either of two points on the axis of a mirror, lens, or other optical system, one point being such that rays diverging from it are deviated parallel to the axis upon refraction or reflection by the system and the other point being such that rays parallel to the […]


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