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प्रश्न
List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision.
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उत्तर
Causes of presbyopia :
Aging
Weakening of ciliary muscles
It is treated by using a bifocal lens both concave and convex.
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संबंधित प्रश्न
Do you know that the corneal-impairment can be cured by replacing the defective cornea with the cornea of the donated eye? How and why should we organise groups to motivate the community members to donate their eyes after death?
A student is unable to see clearly the words written on the blackboard placed at a distance of approximately 4 m from him. Name the defect of vision the boy is suffering from. Explain the method of correcting this defect.
Draw ray diagram for the:-
(i) defect of vision and also
(ii) for its correction.
A person cannot see the distant objects clearly (though he can see the nearby objects clearly). He is suffering from the defect of vision called:
(a) cataract
(b) hypermetropia
(c) myopia
(d) presbyopia
A young man has to hold a book at arm's length to be able to read it clearly. The defect of vision is:
(a) astigmatism
(b) myopia
(c) presbyopia
(d) hypermetropia
What is meant by optical illusion? Give one example.
What is Hypermetropia (far sightedness)?
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.
Choose the Odd One Out:
Nearsightedness : concave lens : : farsightedness : _______
Write scientific reason.
Nearsightedness, this defect can be corrected by using spectacles with concave lens.
