. Elementary chemical microscopy . Fig. 8. Path of Axial Light Rays striking an Irregular Surface. yield diffraction patterns; for as shown in Fig. 8, the light rays b and c, striking reflecting surfaces, are turned aside at such an angle as to preclude their entering the objective. Not infrequently a preparation yields an image consisting in part of a network of fine black irregular lines or of overlapping concentric black circles. It may then be very difficult to decide whether the preparation is actually marked with an intricate pattern or whether the reticulations seen in the image are mer
. Elementary chemical microscopy . Fig. 8. Path of Axial Light Rays striking an Irregular Surface. yield diffraction patterns; for as shown in Fig. 8, the light rays b and c, striking reflecting surfaces, are turned aside at such an angle as to preclude their entering the objective. Not infrequently a preparation yields an image consisting in part of a network of fine black irregular lines or of overlapping concentric black circles. It may then be very difficult to decide whether the preparation is actually marked with an intricate pattern or whether the reticulations seen in the image are merely the result of diffraction patterns. Rotating the preparation by turning the stage (or if the microscope has no rotating stage, turning the specimen) while looking into the microscope will usually greatly aid in clearing up perplexing problems of this sort. Careful consideration of the above described phenomena is absolutely essential to a correct interpretation of the structure of the material being studied. To determine when one is dealing with depressions and when with elevations when working with moderately high powers and vertical or oblique illumination is often a difficult problem which is further complicated for the beginner by the fact that the image seen is that of the object in a completely reversed position. An elevation as seen with the naked eye cast a shadow on the side away from the radiant, that is, the side of the elevation exposed to the source of light will be bright, the other side will
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectmicroscopy, bookyear1
