A Ripple mirror design proposal by David Williams. I've been thinking about Brian White's project to make a reflector arrangement that will continuously reflect sunlight onto a cooking vessel for several hours, despite the sun's movement across (or maybe up or down) the sky. And I've had an idea... Suppose we have what I'll call a "ripple mirror". That's an approximately plane mirror, but with a set of parallel ripples in its reflective surface. The ripples are narrow and shallow, and may be essentially small sectors of cylinders, each subtending about 15 degrees as seen from its central line. It doesn't matter whether the cylindrical surfaces are concave or convex. They might even be alternating, which would mean that the surface would not have any sharp angles.