The light reflection from a substrate seeded with spherical particles is calculated in the approximation that the interaction between the particles can be neglected. In this approximation the problem reduces to that of the light scattering of one sphere on a substrate. The latter problem can be solved using Mie's solution for the scattering by a sphere in a homogeneous medium and an extension of Weyl's method for the calculation of the reflection of spherical waves by a flat surface. The method can be applied to particles with a radius of the order of the wavelength of the incident light. The theory explains in a satisfactory way the results of an ellipsometric experiment with growing spherical mercury particles on a carbon substrate.