The distance between the optical centre of a lens or pole of a spherical mirror and its principal focus.
The distance between a lens or mirror and its focal point. Together with the aperture, the focal length is one of the main properties of a lens or mirror. The longer the focal length, the larger the image scale.
The distance from a lens to the focus point where parallel rays of light hitting the lens are brought together. The focal length of a lens determines its magnification and its field of view, with a shorter length meaning lower magnification but a larger field of view.
Focal length
- terrapin
- terra rossa
- TerraSAR-X
- terrestrial age
- Terrestrial Dynamical Time
- terrestrial magnetism
- terrestrial planet
- terrestrial radiation
- Terrestrial Time
- terric horizon
- terrier
- terrigenous
- territoriality
- territorial justice
- territorial seas
- territory
- terroir
- terrorism
- Terror, Reign of
- Terskol Observatory
- Tertiary
- tertiary
- tertiary alcohol
- tertiary amine
- tertiary colour