(a) N/A
(b) (i) increase in the length of the eye ball, (ii) decrease in focal length of the eye is fully relaxed.
( c) Here, `x = 1.5 m`
For proper vision, `f = - x = -1.5 m`
`P = (1)/(f) = (1)/(-1.5) = -0.67 dioptre`
Negative sign is for concave lens.