(N/A) Following Oersted's observation, scientists conducted significant research:
In $1864$, the laws governing electricity and magnetism were unified and formulated by James Clerk Maxwell, who subsequently realized that light consists of electromagnetic waves.
Radio waves were discovered by Heinrich Hertz and were later produced by $J. C. Bose$ and $G. Marconi$ by the end of the $19^{th}$ century.
A remarkable scientific and technological progress occurred in the $20^{th}$ century, primarily due to an increased understanding of electromagnetism and the invention of devices for the production, amplification, transmission, and detection of electromagnetic waves.