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Question
Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.
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Solution
Myopia is a defect of vision because of which a person is unable to see distant objects clearly but has normal near vision. Myopia occurs because the converging power of the eye lens is greater than normal and the images of distant objects are formed in front of the retina. As a result, a person with myopia cannot see these objects clearly. In certain other cases, myopia occurs because the eyeball is too long and the distance of the retina from the eye lens is large. This, too, causes the formation of images in front of the retina. The far point of a myopic eye is closer than infinity. The following ray diagram explains the myopic eye and how the defect can be corrected by using concave lenses. A concave lens diverges the light rays from distant objects to form virtual images of the objects at the far point of eye. The eye lens then easily focusses the light rays from the far point to form clear images on the retina.
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Due to elongation of _______ and increase in curvature of the eye lens, a person cannot see distant objects clearly.
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- Name the defect shown in the diagram.
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- Name the parts labelled 1 to 4.
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