IV. Intensity of radiation through turbid media

Abstract

In the Bakerian Lecture for this year, which was delivered before the Royal Society on March 4th, on Colour Photometry, we gave incidentally the results of some measurements we had made of the intensity of visible radiation which penetrated through a transparent medium as compared with that which penetrated through the same medium rendered turbid. We showed that the formula deduced by Lord Rayleigh from the scattering of light by small particles was confirmed by our experiments. We thought, however, that the theory might be more fully tested if a larger range of spectrum than that to which we had confined ourselves were used, and at the same time it would be more satisfactory if an instrument possessing no personal equation could be utilised. Our thoughts naturally turned to the thermopile, and more particularly to that form which we described in a previous communication to the Royal Society (“Proc. Roy. Soc.,” vol. 37, p. 157, 1884), since its delicacy was extremely great.