द्वारक

Also known as diaphragm, Aperture

thumb|Different apertures of a lens thumb|In biology, the pupil (appearing as a black hole) of the eye is its aperture and the iris is its diaphragm. In humans, the pupil can constrict to as small as 2 mm (8.3) and dilate to larger than 8 mm (2.1) in some individuals. thumb|A camera aperture thumb|Definitions of Aperture in the 1707 Glossographia Anglicana Nova thumb|Aperture icon