Which leads us to question; Why refraction?
Refraction occurs because ψψ deform first in the direction perpendicular to the medium on impact at the point of incidence.
Why dispersion?
Dispersion occurs when part of the work imparted on ψψ upon collision at the medium boundary remains with ψψ on exit from the medium. When all such work is remove from ψψ when the exit boundary is a reciprocal of the incident boundary, ie the boundaries are parallel, dispersion do not occur.
By symmetry, optimum dispersion occurs when the exit boundary is perpendicular to the incident boundary.
Yes, I will now start my own religion too.