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Why was an electron microscope necessary? Surely at this scale a conventional light microscope would have done the job, wouldn't have needed all these workarounds, and could have recorded live footage of a needle actually playing a record?



It's true that a SEM wasn't strictly necessary, but there are a few interesting features that make SEM images visually different, and perhaps more appealing, than light microscope images. The electron signal emitted by the surface of the objects in the chamber doesn't behave like light bouncing off an object's surface. Normally shadows are cast by photons traveling in straight lines, and our minds have become accustomed to this behavior. The electrons in the SEM can travel in curved paths, so the illumination in the SEM image can effectively go around corners, leading to surreal shadows and highlights.

The aperture size in the SEM is much smaller than that used in a camera or microscope, leading to much higher depth of field for a given geometry and working distance. A camera might be f/16, while this SEM is effectively f/200

The brightness of objects in the image is partially influenced by the material properties and local geometry, so an exposed protrusion or edge will tend to be very bright -- something that doesn't happen with macro photography.

Hey, it's fun to play with scanning electron microscopes.




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