Human eye and working of its lens 50 Words
Answers
The human eye belongs to a general group of eyes found in nature called "camera-type eyes." Just as a camera lens focuses light onto film, a structure in the eye called the cornea focuses light onto a light-sensitive membrane called the retina.
Structure of the eye
The cornea is a transparent structure found in the very front of the eye that helps to focus incoming light. Situated behind the pupil is a colorless, transparent structure called the crystalline lens. A clear fluid called the aqueous humor fills the space between the cornea and the iris.
"The cornea focuses most of the light, then it passes through the lens, which continues to focus the light," explained Dr. Mark Fromer, an ophthalmologist and retina specialist at Lenox Hill Hospital in New York City. [The 7 Biggest Mysteries of the Human Body]
Behind the cornea is a colored, ring-shaped membrane called the iris. The iris has an adjustable circular opening called the pupil, which can expand or contract to control the amount of light entering the eye, Fromer said.
Ciliary muscles surround the lens. The muscles hold the lens in place but they also play an important role in vision. When the muscles relax, they pull on and flatten the lens, allowing the eye to see objects that are far away. To see closer objects clearly, the ciliary muscle must contract in order to thicken the lens.
The interior chamber of the eyeball is filled with a jelly-like tissue called the vitreous humor. After passing through the lens, light must travel through this humor before striking the sensitive layer of cells called the retina.
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