At the 22nd Youth Science and Technology Competition in Chengdu, Zeng Sanzhen, a middle school student in our county, invented the "eye imaging and vision correction principle demonstrator" (as shown in Figure A).
When water is injected into the cavity through the small hole, the rubber film protrudes outward, making the cavity thick in the middle and thin in the edge, which is a convex lens model and can be compared with glasses and convex lenses. When the water in the cavity is pumped out, the middle of the cavity is thin and the edge is thick, which is the model of concave lens;
Therefore, the experimental model can completely simulate the lenses and lenses of glasses;
So the answer is: convex and concave.