The first frame on the left shows a plane wave just after it has been distorted into a wavy shape by the thin-lens term. After this the thin-lens term vanishes.
Subsequent frames show the effect of increasing amounts of diffraction.
Notice the lengthening of the wave packet and the healing of the first arrival. The first frame on the left shows a plane wave just after it has been distorted into a wavy shape by the thin-lens term. After this the thin-lens term vanishes. Later frames show the effect of increasing amounts of diffraction.