LONG SIGHTEDNESS
OR
HYPER METROPIA
SYMPTOMS
In HYPER METROPIA, a person can not see objects clearly which are near to
him, but he can see clearly distant objects
REASON
The reason for HYPER METROPIA is that either the focal length of the lens of
eye is too long or the eyeball is too short.
WHAT HAPPENS IN
HYPER METROPIA
In HYPER METROPIA, light rays from a near object are focused behind the
Retina.
CORRECTION OF DEFECT
This defect can be corrected by using a convex lens of suitable focal length
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POWER OF LENS
Power of lens is defined as the reciprocal of the focal length of the lens in meters.
FORMULA:
Power = 1/f(in meter)
Unit of power of lens is Dioptre.
DIOPTRE
Dioptre is defined as the power of lens whose focal length is one meter if f =1
meter then the power of the lens = 1 dioptre.