FOCALLENGTH
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus. A system with a shorter focal length has greater optical power than one with a long focal length; that is, it bends the rays more strongly, bringing them to a focus in a shorter distance.The above text is a snippet from Wikipedia: Focal length
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focal length
Noun
- The distance at which something (e.g. a lens, mirror etc.) is in focus; in air it is the distance along the optical axis from a "principal plane" of the lens to one of the lens's focal points.
The above text is a snippet from Wiktionary: focal length
and as such is available under the Creative Commons Attribution/Share-Alike License.