Achromatic Lenses consist of two or more elements, usually of crown and flint glass that have been corrected for chromatic aberration with respect to two selected wavelengths. by jay-j
Your are mixing properties. Converging lens is always thicker in the centre and thinner at the edges. The other cathegory is the geometry of shape of the surfaces of the lens. Convex means that the...
The fact that we observe in case of refraction through prism is, the ray gets bent or deviated towards the base of the prism. So in case of a convex lens you can imagine many prisms have been packed...