Lenses and images physics question?

Question

A doctor examines a mole with a 15.0 cm focal length magnifying glass held 13.5 cm from the mole. Where is the image? what is its magnification? how big is the image of a 5.00 mm diameter mole?

Answer 1

The position of the image is:

p = 1 / ((1 / f) - (1 / q))

= 1 / ((1 / 0.15 m) - (1 / 0.135 m))

= - 1.35 m

The magnification of the image is:

M = - q / p

= - 0.135 m / - 1.35 m

= 0.1

If I'm not mistaken, the image is:

0.005 m x 0.1 = 5 x 10^-4 m