A lens is made up of two curved surfaces which can be concave or convex surfaces. When both the surfaces are of the same kind and have the same focal length, they form an equi-convex or equi-concave lens. It has the same radius of curvature on both surfaces. Equi-convex Lenses are a type of convex lenses in which the two opposite curved (spherical) surfaces have the same shape or slope.
