X-ray diffraction pattern is an interference pattern created by x-rays as they pass through a solid material. Studying X-ray diffraction patterns gives detailed information on the three-dimensional structure of crystals, surfaces, and atoms.
Diffraction is the ability of a wave to bend around the edges of obstacles or holes. The effect is most noticeable when the obstacle or hole is comparable to the size of the wavelength
Diffraction grating is a series of slits used to separate an incident wave into its component wavelengths by directionally separating their diffraction maxima.
The regular array of atoms in a crystal is a three-dimensional diffraction grating for short-wavelength waves such as X-rays. The atoms are arranged in planes with interplanar spacing d. Diffraction maxima occur in the incident direction of the wave, measured from the surface of a plane of atoms, and the wavelength λ of the radiation satisfy Braggs’s law:
X-ray crystallography is a determination of a three dimensional arrangements of atoms in a crystal by analysis of X-ray diffraction patterns.
Bragg angle (Θ) is the angle between an incident X-ray beam and a set of crystal planes for which the secondary radiation displays maximum intensity as a result of constructive interference. British physicist Sir William Henry Bragg and his son Sir William Lawrence Bragg developed a simple relation for scattering angles, now call Bragg’s law.
which relates the angle θ between a crystal plane and the diffracted X-ray beam, the wavelength λ of the x-rays, the crystal plane spacing d, and the diffraction order n (any integer).
The diffraction experiment as presently considered is intended to provide quantitative information on the lattice constant and shape characteristics of the unit cell.
Conjugated bonds describe the alternating pattern of double and single bonds, or triple bonds and single bonds, in a molecule. In such molecules, there is some delocalisation of electrons into the pi orbitals of the carbon atoms linked by the single bond.
Global warming or greenhouse effect is an effect occurring in the atmosphere because of the presence of certain gases (greenhouse gases) that absorb infrared radiation. Light and ultraviolet radiation from the sun is able to penetrate the atmosphere and warm the Earth’s surface. This energy is re-radiated as infrared radiation which because of its longer wavelength, is absorbed by such substances as carbon dioxide. The overall effect is that the average temperature of the Earth and its atmosphere is increasing (so-called global Warming). The effect is similar to that occurring in a greenhouse, where light and long-wavelength ultraviolet radiation can pass through the glass into greenhouse but the infrared radiation is absorbed by the glass and part of it is re-radiated into the greenhouse.
The greenhouse effect is seen as a major environmental hazard. Average increases in temperature could change weather patterns and agricultural output. It might also lead to melting of the polar ice caps and a corresponding rise in sea level. Carbon dioxide, from fossil-fuel power stations and car exhausts, is the main greenhouse gas. Other contributory pollutants are nitrogen oxides, ozone, methane, and chloroflourocarbons.
Holography is a technique for creating a three-dimensional image of an object by recording the interference pattern between a light beam diffracted from the object and a reference beam. The image can be reconstructed from this pattern by a suitable optical system.
Crystal lattice is a three-dimensional array of points that embodies the pattern of repetition in a crystalline solid. Don’t mix up atoms with lattice points: lattice points are infinitesimal points in space - atoms are physical objects.
Generalic, Eni. "X-ray diffraction pattern." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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