2.9: Derivation of Magnification
( \newcommand{\kernel}{\mathrm{null}\,}\)
Figure II.14 shows an optical element separating media of indices n1 and n2. I have drawn the element as an interface, though it could equally well be a lens (or, if I were to fold the drawing, a mirror). An image of height h′ is formed at a distance q of an object of height h at a distance p.
Assuming, as ever, that angles are small, we have
magnification=θ2qθ1p.
But Snell’s law, for small angles, is n1θ1=n2θ2, and therefore
magnification=n1qn2p=C1C2.