 The fraction of beam transmitted along the PLA1 axis can be seen by a set of for a given product p0D, where D is the aperture diameter.Eventually, the electron beam becomes totally scattered and lost, but before this happens, a useful amount of electrons is retained in the original focused spot over a finite distance, which can still be used for imaging.This is possible because the removed electrons are scattered and distributed over a broad area like a skirt () surrounding the focused spot.