dispersal -->
dispersion
medical dictionary

<microscopy> The variation of refractive index with colour (or wave-length) of light. The spreading of white light into its component colours when passing through a glass prism is due to dispersion which, in turn, is due to the fact that the refractive index of transparent substances is lower for long wavelengths than for-short wavelengths. A measure of dispersion is defined as: nD - 1 v= nF-nC where nD = refractlve index at 589 nm (yellow), nF = 486 nm (blue), nC = 656 nm (red).

(05 Aug 1998)