Demonstration experiment and theoretical model of light interference with small particles

Abstract This paper explores light interference in physics education and offers a teaching-focused approach to its demonstration experiment and modelling. Light interference is a fundamental wave phenomenon that reveals the nature of light through the redistribution of intensity due to wave superposition. The study highlights the need for simple, accessible methods to improve students’ understanding and address common misconceptions about wave optics. The authors present a demonstration experiment using readily available materials: powdered sugar particles on glass plates of varying thicknesses, and a helium–neon laser ( λ = 0.6328 μ m). This setup enables the observation of interference rings in both reflected and transmitted light, making the phenomenon demonstrable. The theoretical model, grounded in interference principles, provides a comprehensive framework for elucidating the impact of glass thickness and particle radius on ring size. The experimental data demonstrate a correlation between ring size and glass thickness, which is consistent with the predictions of theoretical calculations. From an pedagogical standpoint, the proposed demonstration experiment is uncomplicated, readily accessible, and integrates qualitative and quantitative analysis. It facilitates the development of analytical skills in students by utilising tools such as ImageJ and Mathcad. The implementation of this demonstration experiment can be adaptable to diverse learning levels. It enhances comprehension of the physical nature of the interference phenomenon, stimulates interest in optics, and can be adapted to other powders, including medical powder, talc, and cocoa.