1.

The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem ?

Answer»

SOLUTION :The remedial lens should make the objects at INFINITY appear at the far point.
For object at infinity, `u = - oo`.
Far-point distance of the defected eye, `v = -80 CM`.
By lens formula,
`(1)/(f) = (1)/(v) - (1)/(u) = (1)/(-80) - (1)/(- oo) = -(1)/(80) + 0 = -(1)/(80)`
ORF = - 80 cm.
Power `P = (100)/(f("in cm")) = (100)/(-80) = -1.25 D`.
Negative SIGN shows that the remedial lens is a concave lens.


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