where <math>f</math> is the focal length, and <math>A</math> is the diameter of the aperture.
See also: f-number, numerical aperture
... km² (2.1 mi²) of it is land and 0.6 km² (0.2 mi²) of it is water. The total area is 9.61% water. Demographics As of the census of 2000, there are ...