Abstract: By interpreting the imagery of “moonlight floats over the wilderness” in classical poetry, this paper introduces the Tyndall effect in natural environments and discusses the light scattering phenomena. It furthe analyzes how small particle of varying sizes influence light scattering processes, leading to the establishment of the Mie scattering and the Rayleigh scattering models. The application of thesee models in fluid mechanics optical measurements is also explored, including particle image velocimetry (PIV) and the nano-tracer-based planar laser scattering.