Question: Who developed the first diode??
Answer:
Who developed the first diode?
About 20 years later, John Ambrose Fleming (scientific adviser to the Marconi Company
and former Edison employee) realized that the Edison effect could be used as a radio detector. Fleming patented the first true thermionic diode, the Fleming valve, in Britain on November 16, 1904[13] (followed by  in November 1905).
John Ambrose Fleming