Question
Explain the following with the help of a diagram :
Presbyopia
Presbyopia
✓
Answer
(i) Presbyopia is an age related vision problem. The vision becomes blurred. Because of this old people cannot see nearby objects.
(ii) Generally focusing power of the eye lens decreases with age. The muscles near the lens lose their ability to change the focal length of the lens. The near point of the lens shifts further than the eye.
(iii) Presbyopia can be corrected by using spectacle of convex lens of suitable focal length.
(iv) Sometimes people suffer from nearsightedness as well as farsightedness. In such a case bifocal lenses are required to correct the defect.
(v) In such lenses, the upper part is concave lens and corrects nearsightedness while the lower part is a convex lens which corrects the farsightedness.
(ii) Generally focusing power of the eye lens decreases with age. The muscles near the lens lose their ability to change the focal length of the lens. The near point of the lens shifts further than the eye.
(iii) Presbyopia can be corrected by using spectacle of convex lens of suitable focal length.
(iv) Sometimes people suffer from nearsightedness as well as farsightedness. In such a case bifocal lenses are required to correct the defect.
(v) In such lenses, the upper part is concave lens and corrects nearsightedness while the lower part is a convex lens which corrects the farsightedness.
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