Glass Bead Bow imaged by Matej Gr�k, June '08 in Czech Republic. s are everywhere. Optical effects are everywhere. This 'rainbow' was produced by glass beads in the road surface. Like raindrops, sunlight is reflected once inside them to form a primary bow. There is a difference, glass refracts light more strongly than water and consequently the bow has a radius of only about 21° - half that of a water bow. Tthe 'bow' is bright inside, it is actually a disk. Image ©Matej Gr�k, shown with permission.