Multiple rainbows from single drops of water and other liquids

The scattering of light by spherical drops and the theory of rainbows are reviewed in detail to predict the angular positions of rainbows from single drops. The angular positions of the first 13 rainbows of water, observed from a drop suspended in a student spectrometer, were compared to these theoretical positions. Since the rainbows were dependent on the refractive index, the positions shifted with drops of other fluids having other refractive indices. Light corn syrup yielded 11 rainbows, including the 17th‐order one. The light emerging from the drops was white except for the multicolors of the rainbows and the faint blue of the rays that had been nearly tangentially incident to the drops. With a hand‐held polarized filter, all of the observed rainbows appeared to be polarized parallel to the plane of incidence. Using the 6328‐Å light from a student He–Ne laser, one of the interference patterns composing all natural rainbows was created and photographed. The angular positions of the principal maxima of this pattern differed from the theoretical rainbow positions predicted by geometrical optics by amounts dependent on the drop radius.