What is the focal length of a lens if an object placed 3.28 cm from the lens produces an image that is 4.11 cm in front of the lens?

1.82 cm

Explanation:

The relationship between the object distance (p), image distance (q) and focal length (f) is given by

According to question,

Object distance (p) = 3.28 cm

Image distance (q) = 4.11 cm

Therefore,

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.