microwaves are an example of electromagnetic radiation.
microwaves are an example of what type of energy?
electromagnetic radiation
microwaves do not contain sufficient energy to chemically change substances by ionization, and so are an example of non-ionizing radiation. the word "radiation" refers to energy radiating from a source and not to radioactivity. it has not been shown conclusively that microwaves (or other non-ionizing electromagnetic radiation) have significant adverse biological effects at low levels. some, but not all, studies suggest that long-term exposure may have a carcinogenic effect. this is separate from the risks associated with very high-intensity exposure, which can cause heating and burns like any heat source, and not a unique property of microwaves specifically.
microwave
the development of microwave technology during world war 2, such as the klystron and magnetron tubes and parabolic antennas made radiative (far-field) methods practical for the first time, and the first long-distance wireless power transmission was achieved in the 1960s by william c. brown. in 1964 brown invented the rectenna which could efficiently convert microwaves to dc power, and in 1964 demonstrated it with the first wireless-powered aircraft, a model helicopter powered by microwaves beamed from the ground. a major motivation for microwave research in the 1970s and 80s was to develop a solar power satellite. conceived in 1968 by peter glaser, this would harvest energy from sunlight using solar cells and beam it down to earth as microwaves to huge rectennas, which would convert it to electrical energy on the electric power grid. in landmark 1975 experiments as technical director of a jpl/raytheon program, brown demonstrated long-range transmission by beaming 475 w of microwave power to a rectenna a mile away, with a microwave to dc conversion efficiency of 54%. at nasa's jet propulsion laboratory he and robert dickinson transmitted 30 kw dc output power across 1.5 km with 2.38 ghz microwaves from a 26 m dish to a 7.3 x 3.5 m rectenna array. the incident-rf to dc conversion efficiency of the rectenna was 80%. in 1983 japan launched minix (microwave ionosphere nonlinear interaction experiment), a rocket experiment to test transmission of high power microwaves through the ionosphere.
wireless power transfer