Light scattering and absorption by randomly-oriented cylinders: dependence on aspect ratio for refractive indices applicable for marine particles.

Typically, explanation/interpretation of observed light scattering and absorption properties of marine particles is based on assuming a spherical shape and homogeneous composition. We examine the influence of shape and homogeneity by comparing the optics of randomly-oriented cylindrically-shaped particles with those of equal-volume spheres, in particular the influence of aspect ratio (AR=length/diameter) on extinction and backscattering. Our principal finding is that the when AR>~3-5 and the diameter is of the order of the wavelength, the extinction efficiency and the backscattering probability are close to those of an infinite cylinder. In addition, we show the spherical-based interpretation of extinction and absorption can lead to large error in predicted backscattering.