## Physics: Principles with Applications (7th Edition)

a. The problem describes a magnifying glass used in a way to obtain m= +3.0. This is exactly the problem posed in example 23-13 on page 667. The ray diagram is precisely the same as the scaled diagram shown in Figure 23-43. The image is virtual, upright, and magnified. b. Only a converging lens can make a virtual, upright magnified image. This will be confirmed by calculation; The lens should have a positive power. c. $$m=-\frac{d_i}{d_o}$$ $$d_i=-md_o$$ Use the lens equation. $$\frac{1}{d_o}+\frac{1}{d_i}=\frac{1}{f}$$ Solve for the power, 1/f. $$P=\frac{d_o+d_i}{d_od_i}=\frac{d_o-md_o}{d_o(-md_o)}$$ $$=\frac{0.090m-3(0.090m)} {(0.090m)(-(3) 0.090m)}=7.4D$$