Geissler discharge tube
Quick Summary
A Geissler tube is a gas-filled discharge tube that produces light when an electric current is passed through a rarefied gas within it. These tubes, named after German glassblower Heinrich Geissler, were an early demonstration of the principle behind electric discharge lamps. They typically have a narrowly constricted portion where the luminosity is intensified. The phenomenon of a glow in a gas energized by voltage was first observed in the 17th century, but it was the Geissler tube in 1855 that effectively showcased this principle. Different gases within the tube can produce various colors of light.123
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