frame0=Import["~/courses/Spring2014/MATH089/animations/EMframes00000.gif"]

f0=ImageData[frame0];

Dimensions[f0]

d0=f0[[100,90;;,1]]-f0[[100,90;;,3]];

n=Length[d0]

DataPlot=ListPlot[d0,Joined->True,PlotMarkers->Automatic]

A0=Im[Fourier[d0]];

ListPlot[A0[[1;;20]]  ,Joined->True,PlotRange->All]

h=2 π/n;

uF[x_]:=Sum[A0[[i+1]] Sin[ i h x],{i,1,40}] 2/(Sqrt[n])

FPlot=Plot[uF[x],{x,0,203},PlotStyle->RGBColor[1,0,0]];

Show[{FPlot,DataPlot},PlotRange->All]