Experimental Investigation of Diffraction caused by Transparent Barriers

In addition to wave-particle duality, the contributions of Kirchhoff-Helmholtz are fundamental to the scalar theory of diffraction. The mathematical results of their formulae help predict the maximum intensity of light at the center of the far-field diffraction pattern that coincides with the optical axis. This study demonstrates, via a series of the single-slit experiments, that the Helmholtz–Kirchhoff integral is invalid for transparent barriers. In fact, the experimental results show that the main factors determining the appearance of the diffraction pattern are the refractive index contrast between the barrier and the medium, including the physical invariance of the medium in response to factors such as temperature and pressure, and the dimensions of the barriers.