Topics in Particle and Dispersion Science

Multiple scattering of light in a turbid medium increases effective absorption of light by extending the pathlengths of photons in the medium. This enhances a low absorption of red light by ice and makes deep crevasses in snow, which radiate mostly multiple-scattered light, appear bluish (for example, Bohren CF 1987). The snow in the photo to the left also appears bluish in the shadows. Is multiple-scattering of light in the snow an appropriate explanation of this blue color? Not really, the photo was taken on a cloudless day under a blue sky. In the shadow, the contribution of the blue skylight is dominant. Hence it gives the shadow the distinct blue color.