\(\cfrac{\partial \psi}{\partial x}\cfrac{\partial \psi}{\partial t}=\cfrac{c^2p}{\sqrt{2}}.\cfrac{\partial^2\psi}{\partial x^2}.e^{-i\pi/4}\)
On several occasions where \(\psi\) rests on a parabola contour/generated surface with \(\cfrac{\partial^2\psi}{\partial x^2}=0\) at the focus, the resulting zero coefficient before \(e^{-i\pi/4}\) removes the phase lag and so removes the delay in the change of \(\psi\) in time.
A second focus is possible,
A magnetic coil deformed to provide such a focus will not have a phase lag in its response at the focus also.
This was left unsaid after ultra-bright LEDs, detection points, jet engines, under-water jets, etc.
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