The above figure is Figure 2.5, p. 13, from Schroeder (1987). Applying the equation of paraxial refraction with (air) to each surface gives
Using
Adding (1) and (3) gives
For conjugate points,
As is derived by Morgan,
The ends of the lens are at
References
Morgan, J. Introduction to Geometrical and Physical Optics. New York: McGraw-Hill, p. 57, 1953.
Schroeder, D. J. Astronomical Optics, 2nd ed. San Diego: Academic Press, 1999.
