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Astigmatism

A person can ...

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A person can see clearly only the objects situates in the range of 50 cm to 300 cm. He went to an Optometrist who prescribed him a lens of certain power to increase the maximum distance of his vision to infinity, i.e., it corrected the near sightedness. However, upon using the prescribed lens the person discovered that the near point of his vision has shifted from 50 cm to a distance ‘d’. What is the value of d?

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Q. A short-sighted person has a near point of 15 cm and a far point of 40 cm.
(a) Can he see clearly an object at a distance of :
(i) 5 cm ? (ii) 25 cm ? (iii) 50 cm ?
(b) To see clearly an object at infinity, what kind of spectacle lenses does he need ?

Q. A person can see clearly objects only when they lie between

50

400

cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use, will be?

A person is able to see objects clearly only when they are lying at distances between $50 c m$ and $300 c m$ from his eye.

a. What kind of defect of vision is he suffering from?

b. What kind of lenses will be required to increase his range of vision to infinity?

Q. A far-sighted person has his near point

50 c m

, find the power of lens he should use to see at

25 c m

Q. . A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use, will be A. Concave, -0.25 Diopter B. Convex, -7. 8 Diopter And why image distance(v) is taken as -400 and not -50 but he can see clear object between these two ranges.

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