Question

a person is not able to read from a book until he keeps it at 50cm. determine the power of corrective lens

Answer 1

the power of the corrective lens should be  2 Dioptre.
P = $\frac{1}{f}$
                                               50 cm = $\frac{50}{100} meters$
P = $\frac{1}{ \frac{50}{100} }$
P = +2D