Paulo can see himself in the mirror. The mirror reflects his image back to him. Mateus can't see himself in the wooden chipping board. The wooden surface absorbs light. All objects reflect light or absorb light. The amount of reflection depends on the surface of the object. A piece of paper, for example, is smooth and flat. However, if you looked at a piece of paper under a microscope, you'd see that it actually contains lots of bumps. Because it's surface is not completely smooth, paper absorbs a lot more light than it reflects.
