CHEMISTRY GLOSSARY

Beer’s law    →   Beerov zakon

Beer’s law (or Beer-Lambert law) is the functional relationship between the quantity measured in an absorption method (A) and the quantity sought, the analyte concentration (c). As a consequence of interactions between the photons and absorbing particles, the power of the beam is attenuated from P_o to P. Beer’s law can be written

where A is the absorbance at a given wavelength of light, ε is the molar absorbtivity or extinction coefficient (L mol^-1 cm^-1), unique to each molecule and varying with wavelength, b is the length of light path through the sample (cm), and c is the concentration of the compound in solution (mol L^-1).

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geometrical optics    →   geometrijska optika

In most cases light can be described as an electromagnetic wave. Geometrical optics is an approximation in which the waves can be represented as straight-line rays. This approximation is valid if the light waves do not meet obstacles comparable in size to the wavelength of radiation.

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blackbody radiation    →   zračenje crnog tijela

Blackbody radiation is the radiation emitted by a perfect blackbody, i.e., a body which absorbs all radiation incident on it and reflects none. The primary law governing blackbody radiation is the Planck Radiation Law, which governs the intensity of radiation emitted by unit surface area into a fixed direction (solid angle) from the blackbody as a function of wavelength for a fixed temperature. The Planck Law can be expressed through the following equation

where λ is the wavelength, h is Planck’s constant, c is the speed of light, k is the Boltzmann constant, and T is the temperature.

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Bragg angle    →   Braggov kut

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.

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light scattering    →   raspršenje

Light scattering is a type of diffuse reflection. When light strikes a rough surface, small flat areas are almost comparable to the wavelength, so the light scatters.

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line spectrum    →   linijski spektar

Red-hot gases give line spectrum, i.e. is they emit electromagnetic rays of defined wavelengths. That kind of emission line of spectrum is characteristic of each chemical element.

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microwave radiation    →   mikrovalna radijacija

Microwave radiation is a electromagnetic radiation with wavelength between 3 mm and 30 cm.

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monochromator    →   monokromator

Monochromator (from the Greek words mono and chroma meaning single and colour) is an optical device based on dispersion of light by one or more prisms or diffraction gratings into its constituent wavelengths, which are utilized in turn.

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Rayleigh scattering    →   Rayleighovo rasipanje

Rayleigh scattering is the scattering of light by particles which are much smaller than the wavelength of light.

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diffraction    →   difrakcija

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

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