To understand how a pin hole works (and if mathematics comes easy),
start with Huygens' Principle, then get into Fresnel's Extension.
Basicaly, Huygens stated that every point of a wavefront acts as a point
source becomeing a source of secondary wavelets. Fresnel, more than a
hundred years later, assumed that the secondary waves interfered with
each other according to the principal of superposition. This
interference results in the effect of causing a "focus" of an "image" of
the source of the light ("subject"). Any good optics textbook should
explain the math. The best way to investigate the details of pin hole
properties is with math. Have fun.
Jeff