Light scattering from a birefringent cylinder, spider silk, slimmer than the wavelength approaches dipole radiation.

Using a plane-polarized laser of wavelength lambda = 543.5 or 441.6 nm and spider silk, we investigated the diffraction of a transparent cylinder of diameter D approximately lambda - lambda/5 at normal incidence. The measured pattern corresponded well to the one calculated by a rigorous solution of the theory for the problem. The birefringent index and D of the sample could be determined simultaneously. The experimental data of the scattering cross section for D < lambda/4 suggested that the data approached dipole radiation.