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.
Also called focal distance.
Origin
1745-55
British Dictionary definitions for focal length

focal length

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 in Medicine

focal length n.
The distance from the surface of a lens or mirror to its focal point. Also called focal distance, focus.

focal length in Science
focal length
  (fō'kəl)   
The distance between the optical center of a lens or mirror to its focal point.
focal length in Culture

focal length definition


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.