Name the defect of the eye in which a portion of the object is seen focused while the other portion is blurred.

Astigmatism

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Night-blindness

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Long-sightedness

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Short-sightedness

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Solution

The correct option is A
Astigmatism

Astigmatism is the defect of the eye that arises due to the uneven curvature of the cornea. It is a defect in which a portion of the object is seen focused while the other portion is blurred. It can be corrected by cylindrical lenses. Night-blindness is a condition in which a person feels difficulty in seeing in dim light or during the night. Long-sightedness is where a person feels difficulty in seeing near objects. Whereas in short-sightedness a person feels difficulty in seeing distant objects.

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Similar questions

Astigmatism is an eye defect in which some parts of the object are in focus while others are blurred.

Q. Short-sightedness means that the eye can see the nearby objects clearly and long-sightedness means that the eye can see the distant objects clearly.

(a) What is long-sightedness ? State the two causes of long-sightedness (or hypermetropia). With the help of ray diagrams, show :
(i) the eye-defect long-sightedness.
(ii) correction of long-sightedness by using a lens.
(b) An eye has a near point distance of 0.75 m. What short of lens in spectacles would be needed to reduce the near point distance to 0.25 m ? Also calculate the power of lens required. Is this eye long-sighted or short-sighted ?
(c) An eye has a far point of 2 m. What type of lens in spectacles would be needed to increase the far point to infinity ? Also calculate the power of lens required. Is this eye long-sighted or short-sighted ?

Q. (a) What is short-sightedness? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show:
(i) the eye-defect short-sightedness.
(ii) correction of short-sightedness by using a lens.
(b) A person having short-sight cannot see objects clearly beyond a distance of 1.5 m. What would be the nature and power of the corrective lens to restore proper vision?

Q. Does short-sightedness (myopia) or long-sightedness (hyper -metropia) imply necessarily that the eye has partially lost its abilityof accommodation? If not, what might cause these defects of vision?

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