Derivation formulas for lens essentially traces an arbitrary ray geometrically and mathematically from an object point through the two surfaces of a thin lens to the corresponding image point.
Eight important differences between convex and concave lens are compiled in the article in tabular form. One such difference is the structure of convex lens is like, thicker at the centre and thinner at the edges. Conversely, the concave lenses are thinner at the centre and thicker at its edges, in structure.