Published in Appl. Opt. 56 G88-G97 in 2017
J.A. Lock and G.P. Können
Using ray theory, the Möbius shift of the
(p-1)-order rainbow angle for a
particle having an elliptical cross section is obtained to first order in the
ellipticity as a function of the tilt of the ellipse with respect to the
propagation direction of the incoming rays. The result is then adapted to the
geometry of scattering of light rays from the sun by a falling water drop as a
function of sun height angle. The variation in the angular spacing between the
supernumeraries is determined as a function of location along the rainbow arc,
the conditions under which the rainbow angle is insensitive to drop flattening
were determined, and the dependence of the Möbius shift on the drop refractive
index is shown for rainbows up to fourth order (p = 5).