Demonstrative experiment study on the consistency of two-slit interference and diffraction phenomenon

In the Optics of University Physics, two most important concepts are interference and diffraction, which reflect the wave nature of the light. The corresponding content is relatively abundant, such as Young’s Double-slit Interference, One-slit Diffraction, Grating Diffraction. But they are not easy for undergraduates to comprehend. So in order to show the two phenomenon visually, the related demonstrative experiment equipment are well-developed, but they are independent with each other. The students can accept them separately, but in the same time ignore the connection between them two. Actually, interference and diffraction are consistent in essence from the view of coherent superposition and redistribution of the light intensity. The difference only depends on the specific parameters. The objective of our paper is to analyze the condition for two slits to produce interference and diffraction phenomenon. Also, apply the knowledge of Fourier Optics to analyze the Fresnel diffraction. This would be a good example for the theory of grand unification in physics. Firstly, the intensity distribution is deduced for two-slit interference, one-slit Fraunhofer diffraction, two-slit Fraunhofer and Fresnel diffraction applying complex-amplitude integration method. In the same time, the simulated experimental results by MATLAB are shown. Secondly, the experimental results are given to verify the analysis. Finally, a new idea is presented to realize an equipment of demonstrative experiment for teaching.