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The pupil of the human eye can range in size from 2 mm to over 8 mm to adapt to the environment The human eye can detect a luminance from 10 −6 cd/m 2 , or one millionth (0.000001) of a candela per square meter to 10 8 cd/m 2 or one hundred million (100,000,000) candelas per square meter.
The iris (pl.: irides or irises) is a thin, annular structure in the eye in most mammals and birds that is responsible for controlling the diameter and size of the pupil, and thus the amount of light reaching the retina. In optical terms, the pupil is the eye's aperture, while the iris is the diaphragm. Eye color is defined by the iris.
The pupil gets wider in the dark and narrower in light. When narrow, the diameter be 1.5 to 4 millimeters. [4] In the dark it will be the same at first, but will approach the maximum distance for a wide pupil 3 to 8 mm. [4] However, in any human age group there is considerable variation in maximal pupil size. For example, at the peak age of 15 ...
The macula (/ˈmakjʊlə/) [1] or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around 5.5 mm (0.22 in) and is subdivided into the umbo, foveola, foveal avascular zone, fovea, parafovea, and perifovea areas.
In humans, the cornea has a diameter of about 11.5 mm and a thickness of 0.5–0.6 mm in the center and 0.6–0.8 mm at the periphery. Transparency, avascularity, the presence of immature resident immune cells, and immunologic privilege makes the cornea a very special tissue.
Eye of a European bison Human eye. Complex eyes distinguish shapes and colours. The visual fields of many organisms, especially predators, involve large areas of binocular vision for depth perception. In other organisms, particularly prey animals, eyes are located to maximise the field of view, such as in rabbits and horses, which have ...
Note changes in beam diameter observed on the downstream golden mirror. A natural optical system that has a diaphragm and an aperture is the human eye. The iris is the diaphragm, the pupil is the aperture. In the human eye, the iris can both constrict and dilate, which varies the size of the pupil.
Uranus, when discovered in 1781, was the first planet discovered using technology (a telescope) rather than being spotted by the naked eye. Theoretically, in a typical dark sky, the dark adapted human eye would see the about 5,600 stars brighter than +6 m [6] while in perfect dark sky conditions about 45,000 stars brighter than +8 m might be ...