Definition of “focal length” - English Dictionary

british dictionary

“focal length” in British English

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focal lengthnoun [ C usually singular ]

uk /ˌfəʊ.kəl ˈleŋθ/ us /ˌfoʊ.kəl ˈleŋθ/ specialized

Examples from literature

  • On the other hand, the eye-glass must not be of such small focal length that the image appears indistinct and contorted, or dull for want of light. 
  • The rapidity of a lens depends mainly on its aperture and its focal length. 
  • The speed of a photographic lens depends on the ratio of the effective aperture to the focal length. 
  • To overcome this obstacle to clear vision, and also to secure magnification, the focal lengths of the instruments were greatly extended. 
  • We may apply eye-glasses of different focal length. 

(Definition of “focal length” from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)

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