On the transmission of light through a cloud of randomly distributed particles

The phenomenon of the transmission of light through a cloud of particles distributed at random in a transparent medium is theoretically investigated on the basis of wave-optics. The cases of both transparent and of opaque particles are considered, and it is found that the transmitted beam is progressively attenuated, the intensity diminishing exponentially with the increase in the thickness of the medium. The actual values of the attenuation coefficient are calculated in both cases. It is found that for an opaque particle, the diminution of intensity in the forward direction is actually double what would be expected from simple geometric considerations. For transparent particles, the transmitted intensity shows spectral variations, and this explains some of the phenomena hitherto not well understood, such as the colours shown by the transmitted light, and the complementary nature of this colour and the colour of the light scattered by the cloud in the forward direction