Question

A magnifying glass gives a 4 time enlarged image at a distance of 25cm from the lens. Find the focal length of the lens

Answer 1

We can find the focal length of the magnifying glass from the formula:

$$M=1+\dfrac{d_i}{f},$$ $$f=\dfrac{d_i}{M-1}=\dfrac{25\ cm}{4-1}=8.3\ cm.$$

Answer:

$f=8.3\ cm.$