why the image is not display in the output?

lambda=500e-9; 
k=(2*pi)/lambda; 
a=1e-6;
Io=100.0; 
R=1.0e-3;
Y=(-0.25e-2:1e-5:0.25e-2); Z=Y ; 
I(1:length(Y),1:length(Z))=0;
for i=1:length(Y)
    for j=1:length(Z)
        q=(Y(i).^2+Z(j).^2).^0.5;
        w = 0.05;
        I(i,j)=Io.*exp(-((q.^2)./w^2));
    end
end
imshow(I)

[Ankit]

I think you need to normalize your image by dividing 255.

Answer 1

[Mathieu NOE]

hello

Your I array has not much delta between min (99.5) and max value (100), so you need to help imshow autoscale its range to these min / max values;

figure(1),imshow(I,[]) % grayscale display , zoomed in min / max I range
%   IMSHOW(I,[]) displays the grayscale image I scaling the display based
%   on the range of pixel values in I. IMSHOW uses [min(I(:)) max(I(:))] as
%   the display range, that is, the minimum value in I is displayed as
%   black, and the maximum value is displayed as white.

%%  alternative
figure(2),imagesc(I) ; % automatic image scaling