An old man cannot see objects closer than lm from the eye clearly

CBSE Class 10 CBSE Class 10 Science
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1

An old man cannot see objects closer than lm from the eye clearly. Name the defect of vision he is suffering from. How can it be corrected ? Draw ray diagram for the
(i) defect of vision and also
(ii) for its correction.

2

The person is suffering from Presbyopia. It is a common defect of vision, which generally occurs at old age. A person suffering from this type of defect of vision cannot see nearby objects clearly and distinctively. A Presbyopic eye has its near points greater than 25 cm and it gradually increases as the eye becomes older. Presbyopia is caused by the

  1. weakening of the ciliary muscles
  2. reduction in the flexibility of the eye lens.

This defect can be corrected by using a convex lens of appropriate power.

  1. Ray diagram showing Presbyopia.
    image

  2. Ray diagram showing correction of Presbyopia.

image