Influence of relative refractive index on optical properties of emulsions

The influence of refractive index on the optical properties of 4 wt.% n-hex adecane oil-in-water emulsions with the same droplet diameter (1 mum) and r efractive index (n(d) = 1.43), but different aqueous phase refractive index (n(aq) = 1.33-1.46) was examined in the absence and presence of red dye. A s the n(d)/n(aq) ratio moved away from one (either higher or lower), the sc attering efficiency of the emulsion droplets increased. This caused the emu lsion appearance to go from transparent to opaque, with a corresponding inc rease in spectral reflectance, L-value and turbidity. The spectral reflecta nce and tristimulus values of the dyed emulsions predicted by light scatter ing theory were compared with measured values. The spectral reflectance and L-value predicted by the theory showed similar trends to measured spectra, but the a- and b-values showed opposite trends. Three approaches have been proposed to correct this discrepancy. (C) 2001 Elsevier Science Ltd. All r ights reserved.