An object must be how far from a converging lens (in terms of f) so that the difference between the imag

Question

An object must be how far from a converging lens (in terms of f) so that the difference between the imag

Answer 1

In terms of f, an object should be how close to a converging lens so the distance between Di and f is 1% of the focal length?

1 / Do + 1 / Di = 1 / f ...(1)

Di - f = 0.01f ...(2)

From (2):

Di = 1.01f

Substituting for Di in (1):

1 / Do + 1 / (1.01f) = 1 / f

1 / Do = (1 - 1 / 1.01)(1 / f)

= (1 / 101)(1 / f)

Do = 101f.