Polaroid filter

Suppose a bulk-crystallized polymer sample is observed in an optical microscope with the sample placed between Polaroid filters oriented at right angles to each other. In the absence of any sample, the light would be attenuated owing to the 90° angle between the vectors describing the light transmitted by the two filters. With a crystalline sample of polymer in place, however, a display like... 

Figure 4.12 Spherulites of poly( 1-propylene oxide) observed through crossed Polaroid filters by optical microscopy. See text for significance of Maltese cross and banding in these images. [From J. H. MaGill, Treatise on Materials Science and Technology, Vol. lOA, J. M. Schultz (Ed.), Academic, New York, 1977, with permission.]...

This birefringence coupled with spherical geometry produces light extinction along the axis of each of the Polaroid filters, hence the 90° angle of the Maltese cross. 

If the Polaroid filters are held fixed and the sample rotated between them, the Maltese cross remains fixed because of the symmetry of the spherulite. 

A Polaroid filter allows light through only if the light is polarized at the same angle as the filter. 

Microscope and DLI Apparatus. The apparatus is shown in Figure 1 in block form. A Zeiss Ultraphot II photomicroscope equipped with a polarizer and analyzer, Polaroid filters, and strain-free optics was used to obtain all photographs discussed here. This microscope was modified for... 

Figure 20.66 If two pieces of Polaroid filter are laid at right angles to each other, the light is cut out. This is what is happening at the overlap of the filters here... 

The first programmable computer, the Zl, is developed by Konrad Zuse Sunglasses become polarized by Ray Ban using a Polaroid filter developed by Edwin H. Land Polyst5frene is developed... 

Seventy-five years later, in 1938, Edwin Land invented the sheet polarizer, called H-film, that has been industrialized as the Polaroid filter. Attached to the windows of ships and trains these filters can act as blinds, and they also have been widely used in polarized sunglasses. There was a time when Polaroid filters were considered as antiglare systems for large-scale windshield and headlights of cars [1]. 

Figure 1. Analytical isoelectric focusing of cellulases from Trichodtrma ree-sei. Detection of CBH I and EG I activities using MeUmbLac, in the absence (A) and presence (B) of 10 mM cellobiose. Lane 1, EG I lane 2, EG I (iso-components) lane 3, CBH I (pi 3.9 component) lane 4, EG I-CBH I mixture). Gels were flooded with the fluorogenic substrate (pH 5.0) and after 5-10 min (room temperature) photographed (Polaroid 57, green filter) on a long wavelength UV-transilluminator (8).

The fibers were annealed at 200 C for 5 min. in N2, wound parallel on a sample holder and flat plate X-ray photographs taken by exposing the fibers for 1 h (WAXS) to a beam collimated at 90° to the fiber axis, uatorial diffractometer traces of uniaxially oriented fibers were taken uring slit collimation. WAXS patterns were obtained on polaroid film and the difoctometer traces with a Siemens X-ray system. Nickel filtered CuKa radiation was used. The X-ray unit was operated at 30 KV and 20 mA. The sample to film distance was 71.4 mm. 

Mark the bands of interest with a pencil or photograph the blot using a Polaroid camera equipped with an orange filter. The exposures range from 30-120 s Notes 8 and 9). 

A photograph of the gel can be taken using a bellows-type camera equipped with a Polaroid MP4 system using 3000 iso-Polaroid 667 film. An orange filter is necessary to obtain a good film image. The time of exposure required is 0.5-1 s with a fully opened diaphragm. 

Soak membrane with the POase complexes with reagent and transfer rapidly (within 1 min of wetting) to filter holder, cover with transparent film and take print on instant photographic film (Polaroid Type 612 or 667 from 25 cm) or contact print on blue-sensitive X-ray film. 

The procedure of autoradiography itself is very simple. Dried gel, cellulose acetate or filter paper sheet is covered with X-ray film, clamped between two metal plates and allowed to stand for an appropriate period of time. Then, the X-ray film is developed and zones of the radioactive material are visualized (see also Ref. 232). Also, Polaroid land film can be used for this purpose [223]. 

In the case of visible light, studies of polarization are dominated by the use of dichroic filters (e.g., the Polaroid sheet), for which photons with polarization parallel to a... 

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