The Mie theory of light scattering by a spherical isotropic particle of any radius is briefly described. Equations are given for the angular distribution of intensity, and for the total energy scattered by transparent particles or scattered and absorbed by absorbing particles. It is shown experimentally and by comparison of the equations that both the Mie and the Rayleigh equations for the angular distribution of intensity yield results which are too great by a factor of two when the particle is illuminated by natural light.
Graphs are included giving some of the results of a recently published series of scattering calculations made by The Mathematical Tables Project of the National Bureau of Standards.
A second factor of two occurs in the measurement of the scattering cross section of very large spheres where scattering becomes analogous to diffraction. It is shown theoretically that when the radius of the sphere is at least 25 times the wave-length the scattering cross section is equal to twice the geometric cross section. This result is confirmed experimentally when the observation is made at a distance from the sphere large enough so that the diffracted light is excluded from the measuring device.
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