The separation efficiency of a cyclone has a character of probability. This is to do with the probability of the position of the different particles in the entrance to the cyclone, their chances of separation into the boundary layer flow and the general probability character of turbulent flow. Coarse particles are always more likely to be separated than fine particles. Effectively, the cyclone processes the feed solids by an efficiency curve called the grade efficiency, which increases with particle size.
The video below discusses cyclone performance.
The graph below shows the grade efficiency curve and the reduced grade efficiency curve. The key parameters of the curve can be investigation as to how they effect the link between the curve and the reduced version.