While trying to improve his incandescent lamp, Edison observed something curious: in a vacuum, electrons flow from a heated element (like the filament inside the incandescent bulb) to a cooler metal plate. He patented the finding, even though he could not explore it further. The name given to this phenomenon was, the Edison Effect.
A British scientist named John Ambrose Fleming later made the world’s first radio valve in 1904, based on the Edison Effect: it was called the diode. Two years later, an American named Lee de Forest invented the triode, which became an important part of radio technology paving the way for the wonders of the electronic age.
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