An eye has a near point distance of 0.75 m. What sort of lens in spectacles would be needed to reduce the near point distance to 0.25 m? Also calculate the power of lens required. Is this eye long-sighted or short � sighted?
If an eye has a near point distance of 0.75 m, then convex lenses should be used.
v = -75 m
u = -25 m
⇒ f = 0.375
Hence Power = 1/f = 1/0.375 = +2.67D
Hence, this eye is long-sighted.