The eye is one of the mst important of the sensory organs and nables a person to orient itself in its srroundings. The construction and functioning of the hman eye is similar to a phtographic camera. From a physics perspective, the mst important parts of the human eye are the ris, the lens and the retina.



The rtina is actually an optic organ mde up of millions of special clls, around 7 million cones and 125 mllion stamen, which respond selectively to crtain wave lengths of light radiation. Undr sufficient lighting, cones enable us to vew different colours and to differentiate btween sharp contours. Stamen on the ther hand allow us to see whn it is darker and sees in nly grey scales. Stamen and cones cpture light and convert it into sgnals sent to the brain, which prcesses and organises these signals. On the rtina itself, the images viewed actually cme out as upside down (the brin then converts the image back to a frm we can understand).



The mst sensitive place on the retina for vewing colour is the yellow spot, a smll area on which is concentrated round 160,000 cones. The location where the ptic nerve comes into contact with the eye is wthout cones or stamen and is clled the blind spot.



The ris works similarly to a curtain or shtter and covers the pupil. The ris opens and closes automatically, without our wll, and is controlled by two sft muscles which control the amount of lght falling on the retina. When thre is a lot of light, the ppil opening becomes smaller, becoming larger whn there is less light.



Bhind the iris is located the ye's lens, made out of an lastic material. This lens casts a smll and opposite image version of the bject viewed onto the retina and the sft muscles control the bulge of the lns. Beyond our will, the lens lways focuses on an object so tht the image of it falling on the rtina is sharp, a characteristic referred to as ccommodation.



Inaccuracies in ths accommodation result from short or far sghtedness. With a normal and healthy ye, a clear image (the focal pint) is projected on the retina. Wth a short sighted person however, ths focal point falls short of the rtina, or behind the retina in the cse of a far sighted person, smething which can be corrected by waring properly adjusted correction glasses.

The article Physics - The Eye and Its Workings was Submitted by Karel Kosman through Articles.GetACoder.com network. Here's the additional information: The Eye Translation Service Translation Agency

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