11—Effect of Penetration on Reflectance of Dyed Textile Fibres

The absorption and scatter coefficients, K and S, used by Atherton to define the reflectance of dyed textile materials have been determined on the assumption that fibres of circular cross-section represent the absorbing and scattering elements through which the principal paths of light can be traced. It is shown that the ratio K/S is a function of fibre diameter, dye concentration and extinction coefficient, and the predicted relation is compared with that determined experimentally. The agreement is found to be such as to justify the extension of the theoretical model to a study of the effect of fibre penetration on reflectance of dyed fibres, and the predicted dependence on penetration is found to agree closely with that found in practice. An increase in penetration from 10 per cent to 100 per cent is shown to have the same effect on reflectance as a 33 per cent increase in dye concentration.The effect of fibre refractive index on the reflectance of undyed fibres has has also been estimated.