English: Airy disk. Diffraction pattern of a point light-source seen through a round aperture.

${\displaystyle I(r)=\left({\frac {J_{1}(r)}{r}}\right)^{2}}$

The brightness of the color shows the cube-root of the intensity, since the patterns could hardly be seen at a linear scale. The cube root highly lightens the dark areas, so the rings can be clearly seen, but one must be aware that the rings are much fainter in reality!