The polarized light microscope is designed to observe specimens that are visible primarily due to their optical anisotropic or birefringent features. Polarized light microscopy is perhaps best known for its applications in the geological sciences, which focusses primarily on the study of minerals in rock thin sections. However, a wide variety of other materials can be examined in polarized light, including both natural and industrial minerals, concrete, ceramics, mineral fibers, polymers, starch, wood, urea. The technique can be used both qualitatively and quantitatively with success, and is an outstanding tool for the materials sciences, geology, chemistry, biology, metallurgy, and even diagnostic (gout analysis). Polychromatic light being viewed at the analyser, one specific wavelength will have been removed. This information can be used in a number of ways:
– If the birefringence is known, then the thickness, t, of the sample can be determined
– If the thickness is known, then the birefringence of the sample can be determined
As the order of the optical path difference increases, then it is more likely that more wavelengths of light will be removed from the spectrum. This results in the appearance of the colour being “washed out”, and it becomes more difficult to determine the properties of the sample. This, however, only occurs when the sample is relatively thick when compared to the wavelength of light.