A new approach is developed to estimate the geometrical factors, solid angle approximation and geometrical efficiency
for a system with experimental arrangements using X-ray tube and secondary target as an excitation source in order to
produce the nearly monoenergetic Kα radiation to excite the sample. The variation of the solid angle is studied by
changing the radius and length of the collimators towards and away from the source and sample. From these values the
variation of the total solid angle and geometrical efficiency is deduced and the optimum value is used for the experimental work.