Fraunhofer diffraction

Fraunhofer diffraction is the far-field pattern formed when light waves pass an aperture or obstacle and their incoming and outgoing wavefronts are effectively planar.

Huygens–Fresnel principle: A wave-propagation principle that treats each point on a wavefront as a source of secondary wavelets. It explains how light from different aperture points combines to form the distant field.
Diffraction: The spreading and redistribution of waves when they encounter apertures or obstacles. Fraunhofer diffraction is the far-field regime of this broader wave phenomenon.
Rayleigh criterion: A rule for the minimum angular separation at which two point sources are resolved by an optical system. Its resolution limit is derived from overlap between circular-aperture Fraunhofer patterns.
Fresnel diffraction: Near-field diffraction in which wavefront curvature and propagation distance affect the observed pattern. It retains propagation effects omitted in the Fraunhofer approximation.
Fourier optics: The analysis of optical systems using Fourier transforms of spatial light distributions. Fraunhofer diffraction is the Fourier-transform limit of propagation from an aperture.
Interference: The superposition of waves that produces regions of enhanced or reduced amplitude. Constructive and destructive interference create the bright and dark parts of the pattern.
Diffraction grating: An optical element with repeated grooves or slits that diffracts light into wavelength-dependent directions. Its far-field maxima separate wavelengths according to the grating's periodic structure.
Geometrical optics: An approximation that models light as rays and neglects its wave behavior. It cannot account for the interference fringes that define Fraunhofer patterns.
Aperture function: A spatial function describing the transmission or obstruction of light across an aperture. Its shape determines the Fraunhofer pattern's amplitude and intensity distribution.
Wavelength: The spatial period of a wave, measured between corresponding points in successive cycles. It sets the angular scale of a diffraction pattern for a given aperture.

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