Abstract
We provide measurements of Young’s double-slit experiment using a partially-coherent light source consisting of a helium-neon laser incident on a rotating piece of white paper. The data allow a quantitative comparison with both the standard theory that does not account for the width of the slits, and a full, analytic model that does. The data agree much more favorably with the full calculation.
Highlights
Young’s double-slit experiment is the standard method for demonstrating interference/diffraction in the wave model of light
The detailed structure of the fringe visibility and spacing depends on the complex degree of spatial coherence of the source, and the double-slit arrangement or its extensions can be used to measure coherence aspects of the source
The partially-coherent source is created by expanding a helium-neon laser beam (λ = 632.8 nm) and directing it onto a rotating white index card
Summary
Young’s double-slit experiment is the standard method for demonstrating interference/diffraction in the wave model of light. The detailed structure of the fringe visibility and spacing depends on the complex degree of spatial coherence of the source, and the double-slit arrangement or its extensions can be used to measure coherence aspects of the source. The original experiment of Thompson and Wolf using partially-coherent light presented a theoretical model, along with experimental data recorded on photographic plates [2,3,4]. This model, which we refer to as the standard model, elegantly connects the resulting interference pattern to the complex degree of coherence of the source through the van Cittert-Zernike theorem [5]. The interference fringes are never observed to disappear completely in the experiments, even though this is predicted by the standard model
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