是这样的,书上给了两组图片,一是光学显微镜照的,一是SEM下的,说是较小倍数情况使用光学显微镜更好一些,原因这样解释的:The unaided human eye can easily detect detail only 200 μm.Thus any magnification greater than 1000× only makes the details bigger. WE can not make finer details visible by magnifying the image an extra ten times. An example of this "empty magnification" is shown in Figure6.(即所说的上述两组图片),没看懂,这个empty magnification 是怎么回事。