How can light take every possible path at the same time? In this video, we dive into Feynman’s path integral formulation of quantum mechanics to understand the behaviour of light by applying the approach to single slit and double slit interference.
In the first section, we build an intuitive picture of how a photon “chooses” its path—from every point within a narrow slit to a specific spot on the screen—using a visual rotating arrow analogy. We then work through the mathematics to show how summing over all these possible paths reproduces the classic single-slit diffraction pattern.
In the second section, we extend the approach to the double-slit experiment. By summing contributions from two separate slits, we reveal how quantum interference naturally gives rise to the well-known pattern of bright and dark fringes.
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