Polarimetry

Polarimetry

Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio waves and light. Typically polarimetry is done on electromagnetic waves that have traveled through or reflected, refracted, or diffracted from some material or object in order to characterize that object.

A polarimeter is the basic scientific instrument used to make these measurements, although this term is rarely used to describe a polarimetry process performed by a computer, such as is done in polarimetric synthetic aperture radar.

Polarimetry of thin films and surfaces is commonly known as ellipsometry.

Polarimetry can be used to measure various optical properties of a material, including linear birefringence, circular birefringence (also known as optical rotation or optical rotary dispersion), linear dichroism, circular dichroism and scattering.

To measure these various properties, there have been many designs of polarimeters. Some are archaic and some are in current use. The most sensitive polarimeters are based on interferometers, while more conventional polarimeters are based on arrangements of polarising filters, wave plates or other devices.

Polarimetry can also be included in computational analysis of waves. For example, radars often consider wave polarization in post-processing to improve the characterization of the targets. In this case, polarimetry can be used to estimate the fine texture of a material, help resolve the orientation of small structures in the target, and, when circularly-polarized antennas are used, resolve the number of bounces of the received signal (the chirality of circularly polarized waves alternates with each reflection).

Measuring optical rotation

Optically active samples, such as solutions of chiral molecules, often exhibit circular birefringence. Circular birefringence causes rotation of the polarisation of plane polarised light as it passes through the sample.

A simple polarimeter to measure this rotation consists of a long tube with flat glass ends, into which the sample is placed. At each end of the tube is a Nicol prism or other polarizer. Light is shone through the tube, and the prism at the other end, attached to an eye-piece, is rotated until all light is shut off. The angle of rotation is then read off of a scale. The specific rotation of the sample may then be calculated. Temperature can affect the rotation of light which should be accounted for in the calculations.

External links

* [http://www.gemstonebuzz.com/instruments/polariscope.html Polariscope - Gemstone Buzz] instrument to measure optical properties.


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Look at other dictionaries:

  • Polarimetry — Po lar*im e*try, n. (Opt.) The art or process of measuring the polarization of light. [1913 Webster] …   The Collaborative International Dictionary of English

  • polarimetry — See polarimetric. * * * ▪ chemistry       in analytic chemistry, measurement of the angle of rotation of the plane of polarized light (that is, a beam of light in which the vibrations of the electromagnetic waves are confined to one plane) that… …   Universalium

  • polarimetry — poliarimetrija statusas T sritis Standartizacija ir metrologija apibrėžtis Analizės metodas, pagrįstas optiškai aktyvių medžiagų savybe sukti poliarizacijos plokštumą. atitikmenys: angl. polarimetry vok. Polarimetrie, f rus. поляриметрия, f pranc …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • polarimetry — poliarimetrija statusas T sritis chemija apibrėžtis Analizės metodas, pagrįstas optiškai aktyvių medžiagų savybe sukti šviesos poliarizacijos plokštumą. atitikmenys: angl. polarimetry rus. поляриметрия …   Chemijos terminų aiškinamasis žodynas

  • polarimetry — poliarimetrija statusas T sritis fizika atitikmenys: angl. polarimetry vok. Polarimetrie, f rus. поляриметрия, f pranc. polarimétrie, f …   Fizikos terminų žodynas

  • polarimetry — ˌpōləˈrimə.trē noun ( es) Etymology: International Scientific Vocabulary polar + i + metry : the art or process of using the polarimeter (as in measuring the polarization of light) * * * polarimetry /pō lə rimˈi tri/ noun • • • Main Entry: ↑ …   Useful english dictionary

  • polarimetry — noun see polarimeter …   New Collegiate Dictionary

  • polarimetry — noun a) The measurement of the polarization of electromagnetic radiation b) Analysis using a polarimeter …   Wiktionary

  • polarimetry — Measurement by polarimeter. * * * po·la·rim·e·try (po″lə rimґə tre) measurement of the rotation of plane polarized light by a liquid or solid …   Medical dictionary

  • polarimetry — Смотри Поляриметрия …   Энциклопедический словарь по металлургии

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