Light scattering varies inversely with wavelength. The shorter the wave the
more the scatter. Hence 440 is more sensitive than 660. But absorbance of the
light by the medium is also important. Colorless media abosrb no visible
light: that is why they are colorless. Yellow media absorb in the shorter
range. Therefore you use a longer wave to minimize the false reading of
Absorbance rather than scattering.
