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Numerical aperture (microscopy)
In microscopy, the numerical aperture, AN, of an objective is:
where I is the index of refraction of the medium in which the lens is working (1.0 for air, up to 1.56 for oils), and a is the angular aperture of the lens. It is basically a measure of the diameter of the aperture compared to the focal length. In photography, the f-number expresses the same relationship.
Last updated: 05-25-2005 13:54:45
10-26-2009 08:16:03
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The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details