Problem 5.51

By means of plotting find the positions of focal points and principal planes of aligned optical systems illustrated in Fig. 5.10 : (a) a telephoto lens, that is a combination of a converging and a diverging thin lenses $\left(f_{1}=1.5\right.$ a, $f_{2}=-1.5$ a); (b) a system of two thin converging lenses $\left(f_{1}=1.5 a, f_{2}=0.5 a\right)$; (c) a thick convex-concave lens $\left(d=4 \mathrm{~cm}, n=1.5, \Phi_{1}=+50 \mathrm{D}\right.$ $\left.\Phi_{2}=-50 \mathrm{D}\right)$