We measured the supernumerary spacing parameter of the first- and second-order rainbows of two glass rods, each having an approximately elliptical cross section, as a function of the rod’s rotation angle. We attribute large fluctuations in the supernumerary spacing parameter to small local inhomogeneities in the rod’s refractive index. The low-pass filtered first-order rainbow experimental data agree with the prediction of ray-tracing–wave-front modeling to within a few percent, and the second-order rainbow data exhibit additional effects that are due to rod nonellipticity.
© 2001 Optical Society of America
Charles L. Adler, David Phipps, Kirk W. Saunders, Justin K. Nash, and James A. Lock, "Supernumerary Spacing of Rainbows Produced by an Elliptical-Cross-Section Cylinder. II. Experiment," Appl. Opt. 40, 2535-2545 (2001)