Numerical investigations were performed to assess the effect of "aerodynamic focusing" achievable by varying the angle of approach in the convergence section of a rectangular slit real impactor, at different Reynolds numbers. Computational Fluid Dynamics (CFD) approach was used as a tool in the study. Simulations were performed on a slit impactor in which the angle of approach in the inlet section was varied from 15 degrees to 75 degrees, at three different Reynolds number values namely 200, 1000, and 2000, to characterize the effect of "aerodynamic focusing". It is found from the results of the study that the impactor efficiency curve and cut-point SQRT (Stk)(50) value are strong functions of the above parameters. Aerodynamic focusing effect achievable by varying the angle of inlet convergence section is delineated with appropriate particle tracks. Results of the study are expressed as a surface plot of the cut-point SQRT (Stk)(50) value as a function of the Reynolds number and the angle of approach and a correlation relating the parameters is presented.