Diffraction summary

The diffraction pattern of a single slit is described by the square of a sinc function.

w sinθ = mλ        single slit diffraction minima (w = slit width)

Angular half-width of the central maximum:   θ ~ λ/w

The diffraction pattern of a circular aperture is described by an Airy Disk.

Angular half-width of the central maximum (D = diameter):   θ ~ 1.22 λ/D

The minimum angular separation of two objects which can just be resolved

by an optical instrument is given by θ_min=1.22λ/D.