Astrophysics (Index)About

diffraction

(an effect of the edge of an obstacle on a wave)

Diffraction is an effect on waves that occurs as they encounter an obstacle or opening, i.e., when traveling waves span a limited cross-section. One of diffraction's effects is that some of each wave bends around the edge of the obstacle or opening, proceeding in directions other than the waves' direction while approaching. A result is (an effect like) waves crossing each other with resulting interference. This affects light waves, affecting the resolving ability of telescopes, such that the larger its aperture, the better the angular resolution. A telescope is said to be diffraction limited if all its other optical properties are good enough that the telescope aperture's diffraction is its main limitation in resolving images. Diffraction also affects particles as per quantum mechanics' particle/wave duality. Much effort has gone into characterizing diffraction's effects, theories and models including:

Refraction, on the other hand, is the change in direction of a light ray as it passes between two materials with different densities and is the mechanism of lenses.


(optics,physics)
Further reading:
https://en.wikipedia.org/wiki/Diffraction
https://en.wikipedia.org/wiki/Huygens-Fresnel_principle
https://en.wikipedia.org/wiki/Fresnel_diffraction
https://en.wikipedia.org/wiki/Fraunhofer_diffraction
https://en.wikipedia.org/wiki/Uniform_theory_of_diffraction
http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/diffracon.html
http://electron6.phys.utk.edu/phys250/modules/module%201/diffraction_and_interference.htm
http://labman.phys.utk.edu/phys136core/modules/m9/diffraction.html
http://kestrel.nmt.edu/~mce/Diffraction.pdf
https://www.whoi.edu/cms/files/lecture04_21266.pdf

Referenced by pages:
2D Fourier transform
Airy disk
angular resolution
antenna pattern
aperture
apodization
beam
confusion limit
cosmic dust
diffraction limited
diffraction spike
diffractive interstellar scintillation (DISS)
dirty image
electron scattering
Fabry-Pérot interferometer (FPI)
grating
grism
high-resolution imaging
interference
Lyot coronagraph (CLC)
Lyot stop
neutron scattering
Schiefspiegler
seeing
speckles
spherical aberration
Strehl ratio

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