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प्रश्न
An old man cannot see objects closer than 1 m 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.
उत्तर
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 point 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.
(i) Ray diagram showing presbyopia
(ii) Ray diagram showing correction of presbyopia
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संबंधित प्रश्न
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Draw a neat labeled diagram to show how hypermetropia can be rectified.
Complete the following sentence with appropriate word :
An inability to focus on nearby objects due to loss of elasticity of the lens with age is called Iris.
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(ii) How is the amount of light entering the eye-controlled?
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Observe the following diagram and answer questions following it:
- Identify the defect of vision shown.
- List its two causes.
- Name the type of lens used for the correction of this defect.
