(a) Which parts of the eye cause rays of light to converge on the retina?(b) Which part causes the greatest convergence?(c) Which part brings the image into sharp focus on the retina? How does it do this?
(a) The cornea and the eye lens are the parts of the eye that cause rays of light to converge on the retina.
(b) The cornea is the part of the eye that causes the greatest convergence as the light first enters the eye through the cornea, which is convex in nature.
(c) The eye lens is the part of the eye that brings images into sharp focus on the retina. To produce a sharp image, the eye lens changes its thickness and converging power to focus the images of nearby and distant objects on the retina.
Explanation
Cornea is the front part of the eye-bulging outwards, which is made of a transparent substance, and the outer surface of the cornea is convex in shape. Because of this shape, when the light rays coming from an object enter the eye through the cornea, it just bends or refracts.
Most of the refractive power in the eye comes from the cornea, because of the differences in the indices of refraction between the air (refractive index of about 1.00) and the aqueous humor, which has an index of refraction of 1.34. Around 80% of refraction occurs in the cornea and around 20% in the inner crystalline lens.
Lens or the eye-lens is a convex lens made of transparent, soft, and elastic tissues like a jelly made of proteins, that control the formation of an image on the retina. It is connected with the ciliary muscles that accommodate the eye lens, which means, it changes the shape of the lens to focus the light rays coming from near or distant objects on the retina.
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