Rayleigh scattering 
noun [mass noun] Physics
The scattering of light by particles in a medium, without change in wavelength. It accounts, for example, for the blue colour of the sky, since blue light is scattered slightly more efficiently than red. Compare with Raman effect.This led us to shift the excitation to a lower wavelength to minimize the contribution from Rayleigh scattering in the emission spectra....
- Additionally, there may be significant scattering by the various species present, including Rayleigh scattering by particles smaller than the wavelength of light.
- At these wavelengths, Rayleigh scattering is also reduced, increasing visual clarity.