OPTICS & OPTICAL PHENOMENA A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site rainbow The origins of the primary and secondary rainbows. The concentration of light in the rainbow arcs results from there existing certain preferred angles of deviation for light rays internally reflected within spherical water drops. These angles are about 139° for one internal reflection and about 129° for two internal reflections. Dispersion gives rise to color-fringe effects about the direction of mean deviation and interference effects cause certain other color fringes. The band between the primary and secondary rainbows is noticeably darker than the rest of the sky (Alexander's dark band). An arc of concentric, spectrally-colored rings seen in the sky by an observer looking at rain, mist, or spray with his or her back to the sun. The colors are produced by the refraction and total internal reflection of sunlight by spherical droplets of water. The primary rainbow, with red on the outside and violet inside, results from one total internal reflection. Sometimes a dimmer secondary rainbow with reversed colors is seen, arising from a second total internal reflection.    • OPTICS AND OPTICAL PHENOMENA Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP