1890-1899

Scientists discover and probe x-rays and radioactivity, while inventors compete to build the first radio.

1891

Tesla coil

Nikola TeslaInventor Nikola Tesla, an immigrant to the United States, is granted a patent for the Tesla coil, which would play a role in the development of lighting, radio and other technologies.
1892

Electron theory

Dutch physicist Hendrik Lorentz expands and modifies James Clerk Maxwell's theory of electromagnetism to develop his own electron theory, which would in turn serve as a foundation for Albert Einstein’s theory of relativity.
1894

Cathode rays

The speed of cathode ray emission is measured by English physicist J.J. Thomson and is found to be significantly slower than the speed of light.
1895

Curie's law

French physicist Pierre Curie defends his thesis on magnetism, which includes his experimental findings regarding the effect of temperature on paramagnetism and states what is now known as Curie's law.
1895

X-ray discovery

During experiments with cathode ray tubes, German physicist Wilhelm Roentgen discovers a previously unknown form of electromagnetic radiation, the x-ray.
1895

Hydroelectric power

The first large-scale hydroelectric power plant, located in North America at Niagara Falls, begins delivering power.
1896

AC circuits

A German-American electrical engineer, Charles Steinmetz, applies the mathematics of complex numbers to the analysis of AC circuits.
1896

Zeeman effect

Pieter Zeeman, a student of Dutch physicist Hendrik Lorentz, demonstrates that a magnetic field can split the spectral line of a light source into multiple components with different frequencies (the Zeeman effect).
1896

Radioactivity

French physicist Antoine-Henri Becquerel first observes natural radioactivity.
1896

Radio patented

Italian-Irish inventor Guglielmo Marconi receives a patent for the radio, a device that enables the wireless transmission of electromagnetic waves.
1897

Divisible atom

J.J. Thomson carries out several experiments that lead him to conclude that cathode rays consist of a stream of negatively charged particles much smaller than an atom, dispelling the long-held belief that the atom was indivisible.
1897

Seeing electromagnetism

German physicist Karl Braun invents the cathode-ray oscilloscope, a means of visibly displaying graphical representations of electromagnetic signals. The cathode ray tube that the device contains eventually evolves into other types of electronic displays, including the receiving screen of the television.
1898

Ray research

German physicist Wilhelm Wien determines that the so-called “canal rays” discovered by his compatriot Eugene Goldstein in1886 are the positively charged equivalent of cathode rays.
1898

Telegraphone

Valdemar Poulsen, a Danish engineer, invents the telegraphone, an early magnetic recording device designed to record telephone conversations.
1898

Alpha & beta rays

Ernest Rutherford, a physicist from New Zealand, determines that the rays that Becquerel discovered to be emitted from uranium (1896) are composed of two discrete forms of radiation, which he terms alpha rays and beta rays.
1899

Rechargeable batteries

Waldmar Jungner of Sweden develops the rechargeable nickel-cadmium battery.
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