Dynamic transition between Fresnel and Fraunhofer diffraction patterns - a lecture experiment

Abstract

A simple method for presenting a dynamic transition between Fresnel and Fraunhofer diffraction zones is considered. Experiments are conducted on different apertures and diffraction patterns are photographed at various distances between the screen and the aperture. A diverging lens is introduced into the experimental setup to provide enlarged Fresnel diffraction patterns. Fresnel and Fraunhofer diffraction patterns and dynamic transition between them can be easily obtained on a distance of few meters, what gives an opportunity to use our setup as a lecture experiment. Photographs of transition for square aperture are shown and discussed.