(i) Let the power at the far point be Pf for the normal relaxed eye.
With the corrective lens the object distance at the far point is ∞. The power required is
The effective power of the relaxed eye with glasses is the sum of the eye and that of the glasses Pg.
(ii) His power of accommodation is 4 diopters for the normal eye. Let the power of the normal eye for near vision be Pn.
Then 4 = Pn – Pf or Pn = 64 D.
Let his near point be xn, then