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Polarized Light MicroscopyPolarized light microscopy (PLM) is a technique which employs the use of polarizing filters to obtain substantial optical property information about the material which is being observed. This information can be combined with other microscopy techniques to confirm or elucidate the identity of an unknown material, determine whether a particular contaminant is present (as with asbestos analysis), or to provide important information that can be used to refine a manufacturing or chemical process. PLM was the major microscopy technique in use for identification of materials for nearly a century since its introduction in 1834 by William Fox Talbot, as other techniques such as SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared spectroscopy), XPD (X-ray Powder Diffraction), and TEM (Transmission Electron Microscopy) had not yet been developed. Today, it is still the only technique approved by the Environmental Protection Agency (EPA) for asbestos analysis, and is often the technique first applied for identification of unknown materials. PLM uses different configurations in order to determine different material properties. With each configuration additional clues can be gathered, leading to a conclusion of material identity. With no polarizing filter, the microscope can be used just as a stereo optical microscope, and view qualities such as morphology, size, and number of phases. With a single polarizing filter (single polars), additional properties can be established, such as pleochroism, individual refractive indices, and dispersion staining. With two polarizing filters (crossed polars), even more can be deduced: isotropy vs. anisotropy, extinction angle, birefringence/degree of birefringence, sign of elongation, and anomalous polarization colors, among others. With the use of PLM many of these properties can be determined in a matter of seconds, even for those who are not highly trained. McCrone, a leader in the field of polarized light microscopy, often advised, If you cant determine a specific optical property of a particle after two minutes, move onto another configuration. Since optical properties can be seen so very quickly and easily under polarized light, it is only necessary to spend a maximum of two minutes on a technique to determine a particular property, though often only a few seconds are required.
Document ID
20170000349
Document Type
Other
Authors
Frandsen, Athela F. (Florida Inst. of Technology Melbourne, FL, United States)
Date Acquired
January 11, 2017
Publication Date
January 1, 2016
Subject Category
Chemistry and Materials (General)
Report/Patent Number
KSC-E-DAA-TN37401
Funding Number(s)
WBS: WBS 736466.01.08.06.04
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Keywords
Engineering
PLM
Single Polars
Florida Institute of Technology
McCrone
Polarized
Birefringent
Florida Tech
Internship
Light
Analytical Laboratory
Pathways
Crossed Polars
Microscopy
Polarized Light Microscopy

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