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English version

focal length

From Longman Dictionary of Contemporary Englishfocal lengthˈfocal length noun [countable] technical  the distance between the centre of a lens and the focal point
Examples from the Corpus
focal lengthProperties of a parabola All parabolas are similar. Focal length a determines the magnitude.A single focal length, fixed-focus is often sufficient.The image produced by a diverging lens is however frequently virtual and consequently the focal length does not seem easy to determine.
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