Question

A 3.0 cm-tall object stands in front of a converging lens. It is desired that a virtual image 2.4 times larger than the object be formed by the lens. How far from the lens (in cm) must the object be placed to accomplish this task, if the final image is located 10 cm from the lens?

Answer 1

The distance from the object to the lens that is used in a magnifying glass mode can be calculated from

$$h_{object}/l_{object} = h_{image}/l_{image}$$

to be

$$l_{object} = 10*3/(2.4*3) = 4.17 cm$$