Blue Sun and Moon

Abstract

Paul and Jones¹, discussing the blue sun caused by selective absorption of a cloud of uniform spheres of radius r in light of wave-length λ, have considered the curve relating K (the ratio of effective to geometrical cross-section of a particle) and α, where α= 2πr/λ. They suggest a simple physical explanation of the maxima and minima of this curve on the basis of resonances. The maxima and minima, in the case of small dielectric spheres can also be explained from the principles of physical optics; this point of view was used by Van de Hulst² in considering some aspects of the subject that could not so readily be treated by electromagnetic theory.