The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil. In humans the pupil is round, but other species, such as some cats, have vertical slit pupils, goats have horizontally oriented pupils, and some catfish have annular types. In optical terms, the anatomical pupil is the eye's aperture and the iris is the aperture stop. The image of the pupil as seen from outside the eye is the entrance pupil, which does not exactly correspond to the location and size of the physical pupil because it is magnified by the cornea. On the inner edge lies a prominent structure, the collarette, marking the junction of the embryonic pupillary membrane covering the embryonic pupil.

Read more about Pupil:  Controlling, Optic Effects, Effect of Drugs

Other articles related to "pupil, pupils":

Ca RMetal - Didactic Interest - Assignments
... tools palette (for example, leaving only the intersection and circle tools lets the pupil make compass-only construction) ... teacher chooses the initial objects, the objects to be created by the pupil, and writes a text explaining what is to be done ... Since 2010, when the pupil has finished the construction and wants to test it, random variations are tested (with a tool called Monkey) and a quality note is attributed to the ...
Pupil - Effect of Drugs
... The reverse is true, so control of pupil size is controlled by differences in contraction intensity of each muscle ... Certain drugs cause constriction of the pupils, such as alcohol and opioids ... LSD, MDMA, mescaline, psilocybin mushrooms, cocaine and amphetamines may cause pupil dilation ...
Sian Diamond - Future Characters
2013– Simon Lowsley Richard Mylan Unknown 8x29– 2013– Larry Brown TBA Pupil 9x??– 2013– Lenny Brown TBA Pupil 9x??– 2013– Lisa Brown Caitlin ...
Pupil Magnification
... The pupil magnification of an optical system is the ratio of the diameter of the exit pupil to the diameter of the entrance pupil ... The pupil magnification is used in calculations of the effective f-number, which affects a number of important elements related to optics, such as exposure, diffraction, and depth of field ... For all symmetric lenses, and for many conventional photographic lenses, the pupils appear the same size and so the pupil magnification is approximately 1 ...
Lebanon School District - Budget
... Lebanon School District administrative costs per pupil in 2008 were $743.62 per pupil ... ranked 265th of 500 school districts for per pupil administrative spending ... The lowest administrative cost per pupil in Pennsylvania was $398 per pupil ...

Famous quotes containing the word pupil:

    I am now of all humors that have showed themselves humors
    since the old days of goodman Adam to the pupil age of this
    present twelve o’clock at midnight.
    William Shakespeare (1564–1616)

    All claims of education notwithstanding, the pupil will accept only that which his mind craves.
    Emma Goldman (1869–1940)

    It belongs to the humanity of a master to warn his pupil about himself.
    Friedrich Nietzsche (1844–1900)