focal length

Definition from Wiktionary, the free dictionary
Jump to: navigation, search


Wikipedia has an article on:
The focal point F and focal length f of a positive (convex) lens, a negative (concave) lens, a concave mirror, and a convex mirror


focal length ‎(plural focal lengths)

  1. (optics) The distance at which something (e.g. a lens, mirror etc.) is in focus; in air it is the distance along the optical axis from a "principal plane" of the lens to one of the lens's focal points.