Fundamentals of Physics Extended (10th Edition)

Published by Wiley
ISBN 10: 1-11823-072-8
ISBN 13: 978-1-11823-072-5

Chapter 34 - Images - Problems - Page 1039: 20b



Work Step by Step

Solve the lens equation $$\frac{1}{f}=\frac{1}{p}+\frac{1}{i}$$ for focal length $f$: $$\frac{1}{f}=\frac{i}{ip}+\frac{p}{ip}$$ $$\frac{1}{f}=\frac{i+p}{ip}$$ $$f=\frac{ip}{i+p}$$ Substitute known values of $i=+28cm$ and $p=+40cm$ yields a focal length of $$f=\frac{(+28cm)(+40cm)}{28cm+40cm}=+16cm$$
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