For thin ones, an approximation exists to the formula named for the maker of one.
Gradient-index ones have a variable spatial distribution of indexes. Metamaterials can be used to create "super" ones. These are subject to chromatic and spherical abberation. For thin ones, an approximation exists to the formula named for the maker of one. (*) Converging ones include those that are biconvex. An important feature of them is their focal length. For 10 points, name these optical implements which refract light which can be found in glasses.
Gradient-index ones have a variable spatial distribution of indexes.
lens