Refraction Dispersion (Scalar)
Controls the amount of light dispersion. Dispersion is a phenomenon that causes the separation of a wave into spectral components with different wavelengths, due to a dependence of the wave’s speed on its wavelength. This will cause the surface to render more slowly as it renders each spectral component separately (red, green and blue).
Dispersion as used in this shading model simulates real light dispersion. The higher the value the greater the amount of dispersion that will be simulated and applied.