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प्रश्न
Explain the Term: Astigmatism
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उत्तर
Astigmatism: It is a defect in which some parts of the object are seen in focus while others are blurred. It arises due to the uneven curvature of the cornea. This is corrected by cylindrical lenses.
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संबंधित प्रश्न
Given below is a diagram showing a defect of human eye. Study it and answer the following questions.
(i) Name the defect shown in the figure.
(ii) Give reason for this defect of eye in human being.
(iii) Name the type of lens used to correct the eye defect.
Which defect of vision can be rectified:
by using a concave lens?
An eye has a near point distance of 0.75 m. What sort 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?
Though a woman can see the distant object clearly, she cannot see the nearby objects clearly. She is suffering from the defect of vision called:
(a) long-sight
(b) short-sight
(c) hind-sight
(d) mid-sight
A person is unable to read a book placed closer than 1 meter from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.
Give Reason:
Older people require glasses to read and write.
Draw a neat labeled diagram to show how hypermetropia can be rectified.
What type of lens is used to correct Hypermetropia?
In Myopia the human eye _______.
Match the following:
| Column - I | Column - II |
| 1. Retina | a. Path way of light |
| 2. Pupil | b. Far point comes closer |
| 3. Ciliary muscles | c. near point moves away |
| 4. Myopia | d. Screen of the eye |
| 5. Hypermetropia | e. Power of accommodation |
