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प्रश्न
A person is unable to see objects distinctly placed within 50 cm from his eyes.
(a) Name the defect of vision the person is suffering from and list its two possible causes.
(b) Draw a ray diagram to show the defect in the above case.
(c) Mention the type of lens used by him for the correction of the defect and calculate its power. Assume that the near point for the normal eye is 25 cm.
(d) Draw a labeled diagram for the correction of the defect in the above case.
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उत्तर
(a) The defect of the vision is hypermetropia
Hypermetropia is caused due to:
(i) reduction in the curvature of the lens
(ii) a decrease in the size of the eyeball
(b) Ray diagram:
(c) The corrective lens used for this defect is a convex lens.
Given that the near point of the eye is at 50 cm. The convex lens should form the image of the object placed at the distance 25 cm on the near point of the defective eye.
v = −50 cm
u = −25 cm
`1/"f" = 1/"v"-1/"u"`
⇒ `1/"f"=1/((-50))-1/((-25))=1/50`
Power,`"P"=100/50=+2"D"`
(d) Ray diagram showing the correction of the defect:
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संबंधित प्रश्न
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Which defect of vision can be rectified:
by using a convex lens?
What is the far point of a person suffering from myopia (or short-sightedness)?
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?
Distinguish between the following pair of words:
Myopia and hypermetropia
Have a look at the posture of this woman who is reading a book and answer the questions which follow:
What kind of looking glasses she needs?
The near point of the eye of a person is 50 cm. Find the nature and power of the corrective lens required by the person to enable him to see clearly the objects placed at 25 cm from the eye?
Choose the Odd One Out:
What are the causes of ‘Myopia’?
State reasons for Myopia. With the help of ray diagrams, show the:
- image formation by a myopic eye, and
- correction of myopia using an appropriate lens.
