Analysis of a Thin Optical Lens Model

In this article a thin optical lens model is considered. It is shown that the limits of its applicability are determined not only by the ratio between the thickness of the lens and the modules of the radii of curvature, but above all its geometric type. We have derived the analytical criteria for the applicability of the model for different types of lenses. Quantitative estimations were made for practically important cases ?f a glass lens in air and air lens in water.