The need for information about the thickness of sections used for electron microscopy is the direct result of electron optics, and arises from the fact that the depth of field is such that the whole thickness of the section is focused in the final image. The electron image is, then, a superposition of many profiles from various levels in the section. Analysis of such images requires knowledge of the depth of the specimen in addition to the lateral dimensions displayed in the image. The effect of specimen depth can be considerable in electron microscope images, where structures with dimensions of a few tens of mμ are often studied in sections with thickness in the range of 100 mμ.Therefore, consideration of section thickness is indeed essential for proper interpretation of electron images of sections.
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