option 2 is the right answer because it printing a book and the other ones are science
Answer:
they were authoritarian dictators
Answer: Johann Christopher Denner
Explanation:
In contrast to mechanical waves, electromagnetic waves can travel without a medium. This implies that electromagnetic waves can pass not only through solid objects like air and rock but also through empty space.
James Clerk Maxwell, a Scottish scientist, created a scientific theory to explain electromagnetic waves in the 1860s and 1870s. He realized that electromagnetic waves can be created when magnetic and electrical fields combine together. He compiled this electricity-magnetism relationship into what are now known as "Maxwell's Equations."
German physicist Heinrich Hertz used Maxwell's theories to explain how radio waves are transmitted and received. In honour of Heinrich Hertz, the hertz, or one cycle per second, is the unit of radio wave frequency. Two issues were resolved by his radio wave experiment. First, he had proven that the speed of radio waves was the same as the speed of light, which was something Maxwell had only theorized.
This demonstrated how radio waves are a type of light. Second, Hertz discovered how to create electromagnetic waves by causing the electric and magnetic fields to separate from wires.
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