focal length
noun Optics.
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.
Also called
focal distance.
Origin of focal length
First recorded in 1745–55
Words nearby focal length
British Dictionary definitions for focal distance
focal length
focal distance
noun
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
Medical definitions for focal distance (1 of 2)
focal distance
n.
focal length
Medical definitions for focal distance (2 of 2)
focal length
n.
The distance from the surface of a lens or mirror to its focal point.
focal distance focus
Scientific definitions for focal distance
focal length
[ fō′kəl ]
The distance between the optical center of a lens or mirror to its focal point.