the distance from a focal point of a lens or mirror to the corresponding principal plane. Symbol: f.
the distance between an object lens and its corresponding focal plane in a telescope.
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.
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.
[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.
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 […]