The present paper exploits a full Mie theory, in theory, to study the scattered pattern of parallel monochromatic light passing through the bead-water-aerosol cuvette. In experiment, the bead concentration was adjusted to make the transmission of the light through the cuvette to be about 70%, and the scattering pattern in far field was measured for the angular radius of its first dark ring. The measured angular radius value was compared with those computed theoretically for varying indices of refraction.The best comparison gave the value of the relative index of refraction with respect to that of the pure water. From the refractive index of water, a value of n = 1.6 of the refractive index for these plastic particles were inferred, thereby providing a key optical parameter for these Standard-Matter beads.