The rainbow beam experiment: direct visualization of dipole scattering and optical rotatory dispersion

We show an experiment for the direct visualization of two subtle optical phenomena: optical rotation in a chiral medium and the angular profile of point dipole scattering. By passing a narrowband linear-polarized light beam into a tank filled with a sucrose solution, we see dark and light bands that exhibit the change in polarization state with propagation. This change in polarization state is made visible by the presence of point scattering particles in the liquid which scatter light in the angular profile of elemental dipoles. Using a white light beam for input, this effect generates a wonderful rainbow-like pattern of colors resulting from the medium's optical rotatory dispersion.