Question

What is the focal length of a lens if an object placed 3.28 cm from the lens produces an image that is 1.91 cm in front of the lens?0.828cm-4.57cm-0.219cm1.21cm

Answer 1

Using lens equation:

$\begin{gathered} \frac{1}{f}=\frac{1}{d_i}+\frac{1}{d_o} \\ where: \\ di=1.91 \\ d_o=3.28 \\ so: \\ \frac{1}{f}=\frac{1}{1.91}+\frac{1}{3.28} \\ so: \\ f\approx1.21cm \end{gathered}$

Answer:

1.21 cm