The lateral magnification of a thick centered optical system in air, using the Lagrange theorem in Equation 1.64 and the definition of lateral magnification for a distant object, is given by
assuming that the object and image media are the same (typically air).
The effective focal length of a thick lens or system of lenses is defined by
hence, the lateral magnification with a distant object depends only on the effective focal length F, independently of the particular lens configuration. With this definition, we may see from Figure 3.1 that the effective focal length is the distance from the focal plane ...