How can you tell is a lens is converging or diverging? code example

Example: which lens is converging and diverging

Concave Lens	                                                                               Convex Lens
Concave lens is thinner at the middle and thicker at the edges.	         Convex lens is thicker in the middle and thinner at the edges.
It is a diverging lens.                                                     	It is a converging lens.