function diffract( nSlits)
%-----------------------------------------------------------------------
% diffract: Test superposition of nSlits waves for minima.
%-----------------------------------------------------------------------
if nargin < 1
    nSlits = 2;
end;
f = 1;
tEnd = 5;
t = 0:.01:tEnd;

for phi = 0:.1:2*pi
    signal = sin( 2*pi*f*t);
    plot( t, signal, 'b');
    title("\phi = " + num2str(phi/pi) + "\pi");
    axis( [0 tEnd -1 1]);
    hold( 'on');
    for n = 1:nSlits-1
        signal = signal + sin( 2*pi*f*t - n*phi);
        plot( t, sin( 2*pi*f*t - n*phi), 'b');
        axis( [0 tEnd -1 1]);
    end;
    plot( t, signal/nSlits, 'r');
    axis( [0 tEnd -1 1]);
    pause(.5);
    hold( 'off');
end;

end