cause and correction of defect of vision || physics// in hindi /cbse class 9 10 11 12

The vision becomes blurred due to the refractive defects of the eye. 
There are mainly three common refractive defects of vision. These are
(i) myopia or near-sightedness, (ii) Hypermetropia or far – sightedness, and
(iii) Presbyopia. These defects can be corrected by the use of suitable spherical lenses
concave or convex
for myopia concave lens is used, in hypermetropia convex lens and in Presbyopia bifocal lens is used.

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