1.

Name the three common defects of vision. What are the causes ? Nan1e the type of lens used to correct each of them.

Answer»

Solution :(i) Myopia:
Cause : Elongation of eyeball
TYPE of lens used for correction :Concave ]ens of suitable power
(ii) Hypcrmetropia :
Cause: Shrinking of eye ball
Type of lens used for correction : CONVEX lens of suitable power
(iii)PRESBYOPIA:
Cause: weakening of ciliary muscles
TYPES of lens used for correction : Bifocal lens


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