From waves to bullets: testing Feynman's idea on the two slit experiment

TL;DR

This study tests Feynman's idea that classical objects do not produce observable interference fringes by simulating two-slit experiments with light, demonstrating how coherence and wavelength affect fringe resolution and the observed pattern.

Contribution

The paper provides experimental evidence using light to simulate classical particles and waves, clarifying how coherence and wavelength influence interference visibility in two-slit experiments.

Findings

Dense fringes in coherent light are unresolved, producing a smooth pattern.

Incoherent light with longer wavelengths yields a smooth pattern due to lack of coherence.

Detector resolution and coherence determine the observability of interference fringes.

Abstract

We test the validity of Feynman's idea that a two-slit experiment performed with classical objects (bullets) does not produce observable interference fringes on the detection screen because the Compton's wavelength of the bullets is so tiny, that no real detector could resolve individual interference fringes, thus producing only an average signal which is the observed smooth curve. To test this idea, we study the two-slit experiment in two different situations using light to simulate both wave-like and particle-like bullets. In the first case, we consider coherent light with short wavelengths and in the second case incoherent light with not-so-short wavelength. While in the former case (simulating Feynman's wave-like bullets) the interference fringes are so dense that they cannot be resolved by a detector, therefore resulting in an averaged smooth signal, in the latter case (simulating Feynman's particle-like bullets), although the detector is fully capable of discriminating each fringe, the observed classical smooth pattern limit is produced because of the lack of spatial coherence of the impinging field.