. Biophysical research methods. Biophysics -- Research. 366 OSCAR W. RICHARDS A brightfield microscope without the condenser is used with mono- chromatic light from a sodium or mercury arc (screened with proper filters to isolate the line desired), or tungsten light with an interference filter {, 555 mn) (63), for the examination of the specimen mounted between suitable plates with partially metallized surfaces. Merton states that for practical purposes the method is hmited to a specimen a few microns thick, but this will actually depend on the transparency and optical path differences in
. Biophysical research methods. Biophysics -- Research. 366 OSCAR W. RICHARDS A brightfield microscope without the condenser is used with mono- chromatic light from a sodium or mercury arc (screened with proper filters to isolate the line desired), or tungsten light with an interference filter {, 555 mn) (63), for the examination of the specimen mounted between suitable plates with partially metallized surfaces. Merton states that for practical purposes the method is hmited to a specimen a few microns thick, but this will actually depend on the transparency and optical path differences in the specimen. Surface details and internal detail due to optical path differences may be visualized with the interference microscope, but it has been too little used with biolog- ical materials to suggest what will be its ultimate contributions and limitations. I. TRANSPARENT AND SLIGHTLY ABSORBING SPECIMENS—PHASE MICROSCOPY Phase microscopy utilizes optical path and absorption differences in the microscope to increase or decrease, or reverse and increase or decrease, the contrast in the image from transparent specimens hav- ing optical path differences, or of low absorption contrast (Fig. 9).. Fig. 9. Wheat chromosomes stained with acetocarmine: (A) brightfield microscope; (B) dark contrast; (C) bright contrast; (D) bright contrast plus red filter with phase microscope. The method is applicable to living unstained cells and tissues, crystals, colloids, natural and artificial fibers, surface and internal detail of glass and plastics, minerals, stained or colored materials of low con- trast, and replicas of surfaces (39,40).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Uber, Fred Murray, 1905-. New York : Interscience Publishers
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