An opaque disk with a circular aperture at its centre. Diaphragms of different sizes are used to control the total light flux passing through an optical system or to reduce aberration by restricting the light passing through a system to the central portion. An iris diaphragm consists of a number of overlapping crescent-shaped disks arranged so that the central aperture can be continuously varied in diameter.
Electronics and Electrical Engineering
1. A vibrating membrane used in sound transducers such as microphones and loudspeakers.
2. A porous partition in an electrolytic cell that separates the electrolytes while allowing ions to pass through.
Biology
The muscular membrane that divides the thorax (chest) from the abdomen in mammals. It plays an essential role in breathing (see alsorespiratory movement), being depressed during inspiration and raised during expiration.