Eye : Blinking
This article refers to the sight organ. For other usages of the word "eye", see Eye (disambiguation).(See also vision.)
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Image of a human eye. Note that not all eyes have the same anatomy as a human eye. |
Light from a distant object and light from a near object being brought to a focus |
An eye is an organ capable of detecting light. The simplest eyes simply detect whether the surroundings are light or dark. Compound eyes are found among the arthropods (insects and kin), and are composed of many simple facets which give a pixelated image (not multiple images as is often believed). In most vertebrates and some mollusks the eye works by projecting images onto a light-sensitive retina, where the light is detected and transmitted to the brain via the optic nerve. The eye is typically roughly spherical, filled with a transparent gel-like substance, with a focusing lens and often a muscle called the iris that controls how much light enters.
Focusing
In order for light rays to be brought to a focus they must be refracted. The amount of refraction required depends on the distance of the object which is being viewed. A distant object will require less bending of light than a nearer one. Most of the refraction occurs at the cornea[?] which has a fixed curvature. The remainder of the required refraction occurs at the lens. The lens can be pulled flatter or rounder by muscles, which adjust the power of the lens.==Parts of the eye==:
Problems:
See also:
Hardy
it was by no means a large one, and the increasing expenses of his
His father had been possessed of a small private fortune, but had
death had left about fifteen thousand dollars to his son. This sum
the time might come when it would, for his children's sake, be
had abstained from taking any step until his sons were of an age to be
prairies.
Frank Hardy, at the time our story begins, was about forty. He was
had hardened his muscles, and given him the full use of every
looked thirty years old. She was a high-spirited woman, well fitted
settler's life.
The subject of emigration once started, was frequently continued,
advantages and disadvantages of the various countries and colonies
Argentine Republic, in its magnificent rivers, its boundless extent
probable prospects, offered the greatest advantages.
The decision once arrived at, it was determined to announce it to
decided upon. Breakfast was over, and the boys, whose holidays had
"Wait a moment, boys; there is something we want to talk to you
what you boys are to become, and we do not see any openings likely
fights with Indians, and all that sort of thing. Oh, it would be
shall have fights with Indians, nor do think.html">think it would be very jolly
would have to work hard, to help me in everything, and to look after
all things in the world."
"And what do you think of it, Maud and Ethel?" their mamma asked
doubtful as to the pleasure of the fights with Indians which their
very useful little women, and will have to help me just as the.
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