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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
Name one defect of vision (or eye) which cannot be corrected by any type of spectacle lenses.
Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
What type of lenses-converging or diverging-would an optician prescribe for her?
Name the defect of vision which can be corrected by a diverging lens. Show clearly by a ray diagram how the lens corrects the defect.
Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.
Differentiate between members of the following pair with reference to what is asked in the bracket.
Rods and cones (sensitivity).
Enumerate the common defects of vision, their causes and the possible methods of correcting them.
In Myopia the human eye _______.
Assertion: Concave mirrors are used as reflectors in torches, vehicle head lights and in search lights.
Reason: When an object is placed beyond the center of curvature of a concave mirror, the image formed is real and inverted.
Which of the following statement is correct?
A person needs a lens of power –4.5 D for correction of her vision.
- What kind of defect in vision is she suffering from?
- What is the focal length of the corrective lens?
- What is the nature of the corrective lens?
