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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.
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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
In a Std. X class out of 40 students 10 students use spectacles, 2 students have positive power and 8 students have negative power of lenses in their spectacles.
Answer the following questions:
(1) What does the negative power indicate?
(2) What does the positive power indicate?
(3) Generally which type of spectacles do most of the students use?
(4) What defect of eyesight do most of the students suffer from?
(5) Give two possible reasons for the above defect.
Explain two possible reasons of myopia. How can it be corrected? Explain with a suitable diagram.
Name any two defects of vision which can be corrected by using spectacles.
You do not enjoy watching a movie from a very short distance from the screen in a cinema hall. Why?
Choose the correct answer :
Presbyopia is a disease of _____________
Draw a neat labeled diagram to show how hypermetropia can be rectified.
What type of lens is used to correct Hypermetropia?
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.
Mention, if the following statement is True or False
Hypermetropia is a defect of the eye caused due to the eyeball elongation
Choose the Odd One Out:
