Ray diagrams:

          Ray diagrams are drawings of the different situations for lenses.  These drawings are the different cases for a double convex lens.

          For the ray diagrams, assume that the lenses are thin.  We assume this because we do not want the thickness of the lens to affect the bending of the rays.  Although the rays do bend when they enter and leave the lens, it is miniscule and for the most part can be neglected.

Ray diagrams for a double convex mirror

(Click for see the image)

Case 1 – Object is at infinity
Case 2 – Object beyond 2F
Case 3 – Object at 2F
Case 4 – Object between F and 2F
Case 5 – Object at F
Case 6 – Object between F and the lens