Single-slit diffraction and the Heisenberg principle for position and momentum
Monochromatic light is prepared by a single slit of spatial width Δx. The diffraction pattern is considered to obtain the corresponding probability density of the momentum. Let P be the probability weight to measure a momentum in a finite window of width Δp. For small Δp the asymptotic law P ~ ΔxΔp/h is verified, while h is Planck's constant of action.
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