Microwave ovens turn electric energy into electromagnetic waves that heat food by stimulating molecules to vibrate and build up thermal energy. While the term “radiation” may have negative connotations, these are nonionizing electromagnetic waves, just like light or the radiation you feel when touching a metal object.
When a microwave is turned on, the magnetron generates microwaves, which travel through a waveguide to reach the cooking cavity. The magnetron rotates at a precise speed to expose all parts of the food to the microwaves, which helps ensure even heating and faster cooking.
The microwaves hit the water molecules in foods, which start to warm up quickly. They also heat sugars and fats, but to a lesser degree. The microwaves only penetrate the food inside the oven; they don’t radiate out into the air, so your kitchen doesn’t get hotter while you cook.
The first microwave oven was developed by Percy Spencer for Raytheon during World War II. His experiment with radar research involved a magnetron that generated microwaves. When he walked by it and placed a candy bar and egg on top, the microwaves melted the candy bar and exploded the egg. Spencer patented his invention in 1945.
Today, microwaves are an essential part of modern technology. They are used in point-to-point communications systems for voice, data and video, for wireless networks, for microwave radio relay networks, for radar, satellite and spacecraft communication, medical diathermy and cancer treatment, spectroscopy and industrial heating. They also play an important role in collision avoidance systems, garage door openers and keyless entry systems. Microwaves are the basis for the cosmic microwave background radiation that fills the universe, and provides clues about the Big Bang.