Some reflector telescopes have one or more convex secondary mirrors, most notably the Cassegrain and Schmidt camera types, but all have a concave primary mirror. Concave mirrors cause the reflected light to converge to a common focal point, while convex mirrors cause the rays to diverge, or spread apart. Don't confuse diverging with diffusing, however. Both types of mirror create specular reflections - which is a fancy term meaning you can see images in the reflections. Diffuse reflectors, such as paper, do not produce images.