If you look closer in the magnifying glass, you notice that the glass curves on both sides. This is called a convex. The opposite of a convex is a concave. Then it bends inward instead of outward. When light goes through a convex shape, such as in the magnifying glass, it hits the majority of the retina in the back of the eye. In this way, the eye is tricked into seeing one thing bigger than it actually is.