Found 1 items, similar to Focal distance or length of a lens or mirror.
English → English (gcide) Definition: 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]