ψ is circular It is wrapped around a circle of perimeter 2πr, where r is the radius from the particle center, travelling at light speed c. On every cycle of period T=1f, it traveled once along the perimeter and has rotated by 2π rad. It is then better to redefine light speed with consideration for the value of π,
c=π∗108
instead of
c=2.99792458∗108
such that r is defined/measured without the uncertainty associated with the value of π.
π at light speed will be quite a splat.