Question

Without glasses, your Uncle Albert can see things clearly only if they are between 20 cm and 180 cm from his eyes. Part A What power eyeglass lens will correct your uncle's myopia? Assume the lenses will sit 2.0 cm from his eyes. Part B What is your uncle's near point when wearing these glasses?

Answer 1

a )by using the lens formula

1 / f = 1 / d o + 1 / di

where

d o =  2.0 cm =0.020 m , di =  180 cm = 1.88 m

1/f = 1/ ( - 0.020 - 1.88 )

= - 0.5263 diopte (where   The refractive power
                    P = 1/ f )

b )  1/ d_o =   1/ f - 1/ d₁   

= [1/ ( - 0.020 - 1.88 ) ] - [( 1 / -0.20 - 0.020 ) ]

= - 0.5263 + 4.454

= 4.019 m

di = 0.2488 m = 248.8 cm