I have a question. In regards with the given computation,

```
u0(r_, phi_) := Sum(I^(-n) BesselJ(n, r) Exp(I n phi), {n, -5, 5});
{Plot3D(Re(u0(r, phi)), {r, 0, 4}, {phi, 0, 2 Pi},
ColorFunction -> Hue),
Plot3D(Im(u0(r, phi)), {r, 0, 4}, {phi, 0, 2 Pi},
ColorFunction -> Hue)}
{Plot3D(Abs(u0(r, phi)), {r, 0, 4}, {phi, 0, 2 Pi},
ColorFunction -> Hue, PlotRange -> All),
Plot3D(Arg(u0(r, phi)), {r, 0, 4}, {phi, 0, 2 Pi},
ColorFunction -> Hue, PlotRange -> All)}
```

which is in Cartesian coordinates, the magnitude of the series for the plane wave must be constant 1. How do I set this in the given code?

Thanks