The rapid development of the method of physical optics dictates the need for an adequate assessment of the lower limit of applicability of this method. It is generally accepted that the method is adequately applicable to particles larger than 10μm, but no detailed studies have been carried out so far due to the high computational complexity of the exact numerical methods required to obtain reference solutions.

This paper presents the results of a comparison of solutions obtained by the method of physical optics with the Discontinuous Galerkin Time Domain method. The incident radiation wavelength was taken to be 0.532μm, the refractive index was 1.3116, and the particle size was 20μm. A particle of a random polyhedral shape with a random orientation in space was considered.