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प्रश्न
List three common refractive defects of vision. Suggest the way of correcting these defects.
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उत्तर
The three common refractive defects of vision are as follows:-
Myopia (short-sightedness):- It is corrected by using spectacles having concave lenses of appropriate power.
Hypermetropia (far-sightedness):- It is corrected by using spectacles having convex lenses of appropriate power.
Presbyopia:- This defect is corrected using bifocal lenses of appropriate power in which the upper part consists of a concave lens (to correct myopia) and the lower part consists of a convex lens (to correct hypermetropia).
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संबंधित प्रश्न
What is the other name for
hypermetropia
Where is the near point of a person suffering from hypermetropia (or long-sightedness)?
Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.
The near-point of a person suffering from hypermetropia is at 50 cm from his eye. What is the nature and power of the lens needed to correct this defect? (Assume that the near-point of the normal eye is 25 cm).
The defect of vision in which the eye-lens of a person gets progressively cloudy resulting in blurred vision is called:
(a) myopia
(b) presbyopia
(c) colourblindness
(d) cataract
Explain the terms ‘adaptation’ and ‘accommodation’ with reference to the eye.
Select the odd one in the following series:
Endolymph, Tympanic membrane, Semi-circular canal, Blind spot.
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.
What are the causes of ‘Myopia’?
