Electron Microscope Lens

This is the "Lens" of a disused Transmission Electron Microscope. Unlike optical lenses, which work because they consist of material with a refractive index that is different to air, this lens is simply a hole in a large coil of copper wire (about a hand-span in width, and about an inch thick). By applying a current to the wire, a beam of electrons flying through the central hole can be narrowed or broadened, similar to the way light beams are altered when they pass through an optical lens. The application of this type of lens in the first working electron microscope won Ernst Ruska the Nobel Prize in Physics in 1986. A fantastic explanation of how these lenses work can be found here .

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