Answer
(a) increase
(b) $1.33cm$
Work Step by Step
(a) We know that the focal length and refractive power are inversely proportional. When our eyes focus on a close-up object then the focal length of the eye lens is decreased and as a result the refractive power is increased.
(b) We can calculate the required focal length of the eye for a near object as follows:
$f_{close}=\frac{1}{\frac{1}{f}+P}$
We plug in the known values to obtain:
$f_{close}=\frac{1}{\frac{1}{0.017m}+16diopters}$
$f_{close}=\frac{1}{74.82}m=0.0133m=1.33cm$
