(*intensity formula for 2D rectangular aperture*)
intensity[x_,y_,a_,b_] = Sinc[a x]^2 Sinc[b y]^2;

(*square aperture, a=b=1*)
Plot3D[intensity[x,y,1,1],{x,-10,10},{y,-10,10},PlotRange->{0,1}, PlotPoints->100]
DensityPlot[intensity[x,y,1,1],{x,-10,10},{y,-10,10},PlotRange->{0,1}, PlotPoints->100]
Plot3D[intensity[x,y,1,1],{x,-10,10},{y,-10,10},PlotRange->{0,0.05}, PlotPoints->100]
DensityPlot[intensity[x,y,1,1],{x,-10,10},{y,-10,10},PlotRange->{0,0.05}, PlotPoints->100]

(*rectangular aperture, a=1; b=2.5*)
Plot3D[intensity[x,y,1,2.5],{x,-10,10},{y,-10,10},PlotRange->{0,1}, PlotPoints->100]
DensityPlot[intensity[x,y,1,2.5],{x,-10,10},{y,-10,10},PlotRange->{0,1}, PlotPoints->100]
Plot3D[intensity[x,y,1,2.5],{x,-10,10},{y,-10,10},PlotRange->{0,0.05}, PlotPoints->100]
DensityPlot[intensity[x,y,1,2.5],{x,-10,10},{y,-10,10},PlotRange->{0,0.05}, PlotPoints->100]

(*rectangular aperture, a=1; b=25*)
Plot3D[intensity[x,y,1,25],{x,-10,10},{y,-10,10},PlotRange->{0,1}, PlotPoints->300]
DensityPlot[intensity[x,y,1,25],{x,-10,10},{y,-10,10},PlotRange->{0,1}, PlotPoints->300]
Plot3D[intensity[x,y,1,25],{x,-10,10},{y,-10,10},PlotRange->{0,0.05}, PlotPoints->300]
DensityPlot[intensity[x,y,1,25],{x,-10,10},{y,-10,10},PlotRange->{0,0.05}, PlotPoints->300]

(*intensity formula for double slit in x, single wide slit in y*)
(*x dimensions: slit width a = 1, slit separation d = 4*)
(*y dimensions: slit width b=25*)
intensity2[x_,y_] = Sinc[ x]^2 Cos[4 x]^2 Sinc[25 y]^2;

Plot3D[intensity2[x,y],{x,-10,10},{y,-10,10},PlotRange->{0,1}, PlotPoints->300]
DensityPlot[intensity2[x,y],{x,-10,10},{y,-10,10},PlotRange->{0,1}, PlotPoints->300]
Plot3D[intensity2[x,y],{x,-10,10},{y,-10,10},PlotRange->{0,0.05}, PlotPoints->300]
DensityPlot[intensity2[x,y],{x,-10,10},{y,-10,10},PlotRange->{0,0.05}, PlotPoints->300]