where <math>f</math> is the focal length, and <math>A</math> is the diameter of the aperture.
See also: f-number, numerical aperture
... -72.577131)1. According to the United States Census Bureau, the town has a total area of 20.0 km² (7.7 mi²). 11.4 km² (4.4 mi²) of it is land and ...