Hello Gianni, Thank you for your clarification of the matter of the bead-and-hole shadow caster. Your plottings of the light distributions should help to convince some disbelievers as to the physical mechanism of the formation of the shadows.
At the time of posting this note, I also will forward a copy of a message I sent on May 6, of 1999, re this topic. Perhaps you will notice the "volcano" analogy for the 3-dimensional light distribution and compare it mentally to the imagined solids described by revolution of your light antensity profiles about their vertical axes of symmetry? Sciagraphically, Bill Maddux