The Human Eye (biology)The pupil is an opening which allows light to pass into the eye. It isthe dark hole in the center of your eye. The pupil is controlled bythe iris (the colored part of the eye) which is a muscle that contractsto make the pupil smaller and relaxes to allow the pupil to widen.The pupil’s size relates to how much light there is in a particularsetting. The iris is covered by the cornea. The lens of the eye islocated in back of the iris. The lens focuses the light onto the retina,which acts like a screen. Eyelashes and eyelids protect the eye bystopping dust particles from falling onto the eye itself.
The Human Eye (biology)There are two types of light sensitive cells on the retina.Rods, are used for black and white vision, and areconcentrated on the sides of the retina. Cones are used forcolor vision, and are concentrated in the center of theretina. Vision is most acute in the area of the retina knownas the fovea centralis.
The Human Eye (Physics)In our eyes, the object is beyond 2F, and the image formedis real, inverted, smaller than the object, and on theopposite side of the lens. We know that the image formedmust be real, because it is projected onto the retina (whichis like a screen). However, we don’t actually “see” theobject as inverted because our brain flips things around sothat we see them as being upright.
The Human Eye (Physics)We know that lenses are needed to focus an object onto ascreen, and in this case the retina. One of the theories ofhow the eye focuses is the 3 lens system. In this situation,(1) the cornea would have little refractive power, and justserve as a “cover glass” to the eye. (2) The aqueous lens lieson top of the pupil, and has a strong refractive power,because it is a very thick lens. (3) The vitreous lens does alot of magnification.
Other factsIts index of refraction The blind spot, locatedchanges because there is where the optic nervea density change within meets the eye, containsthe lens itself. no photo-receptors. Some animals have literal colour blindness. They do not have cones on their retinas.
Sources:Saskatchewan Education. (1992). Science: ACurriculum Guide for the Secondary LevelPhysics 20/30Oracle Quest. Retrieved fromhttp://library.thinkquest.org/C003776/ingles/print/chapter5.htm