diffract

Diffract is a verb describing the action of a wave bending and spreading as it encounters an obstacle or passes through a narrow aperture. The term is used across wave phenomena, including light, sound, water waves, and matter waves such as electrons and neutrons. The word derives from Latin diffrangere, meaning to break apart, and was adopted to describe how waves spread beyond barriers or around edges.

Mechanism and description: Diffraction is commonly explained by the Huygens-Fresnel principle, which treats every point on a wavefront as a secondary source of wavelets. The superposition of these wavelets produces the observed field, with interference between them creating regions of enhanced or diminished intensity. The resulting patterns depend on wavelength and geometry of the obstacle or aperture. In optics, diffraction is often discussed in terms of single-slit, double-slit, and diffraction-grating configurations, each producing characteristic interference fringes.

Examples and related concepts: A narrow slit produces a central bright maximum flanked by minima; two closely spaced slits create a clear set of fringes; diffraction gratings separate light into its component wavelengths. Diffraction phenomena are not limited to light; they are observed in sound and water waves and are also signatures of wave–particle duality in quantum matter.

Applications and significance: Diffraction sets fundamental limits on optical resolution, described by criteria such as the Rayleigh criterion. Diffractive optics use engineered structures to shape wavefronts for lenses and imaging. In science, diffraction patterns of X-rays, electrons, and neutrons reveal crystal structures and atomic spacings, while Fourier analysis provides a mathematical framework for interpreting diffraction data.