Question

0 Accepted characters An object is located 1.50 m from a 6.5-D lens. (a) By how much does the image move if the object is moved 0.90 m closer to the lens? (b) By how much does the image move if the object is moved 0.90 m farther from the lens?

Answer 1

Solution :-

given,

power of lens = 6.5 D

diopter = 1 / focal length

6.5 = 1 / focal length

focal length = 1 / 6.5

focal length = 0.1538 m

by lens equation

1 / f = 1 / do + 1 / di

1 / 0.1538 = 1 / 1.5 + 1 / di

di = 0.1714 m

if the object is moved 1.0 m closer to the lens

1 / 0.1538 = 1 / (1.5 - 1) + 1 / di

di = 0.2221 m

so,

image will move by = 0.2221 - 0.1714

image will move by = 0.0507 m or 5.07 cm

if the object is moved 1.0 m farther from the lens

1 / 0.1538 = 1 / (1.5+ 1) + 1 / di

di =0.1639m

image will move by = 0.1714 - 0.1639

image will move by = 0.0075 m or 0.75cm