Microwave ovens have their roots in radar research before and during the Second World War. Engineers at the Raytheon Company, a U.S. defense contractor, built a large magnetron, a device that generates microwaves, as part of this research. As an engineer named Percy Spencer walked past the device, he noticed that the radiation from the machine melted his candy bar. Intrigued, he then used the magnetron to cook popcorn and an egg. Spencer attached the magnetron to a metal box, leading to the birth of the first microwave oven. In 1945, Spencer patented the microwave oven.
So, how do microwave ovens work? Microwave ovens cook food by injecting the food with microwaves. Microwaves are electromagnetic waves that are invisible to the human eye and fall between radio waves and infrared waves. They bounce around in the metal box that is a microwave oven and cook food through a process known as radiation heating. Essentially, microwaves excite the molecules within an object by lodging themselves in the water, sugars, and fats.
Microwave ovens heat the food’s insides, reducing the cooking time. Something that would take hours to bake in a conventional oven can cook in a couple of minutes in a microwave oven. However, certain foods cook better than others. Foods that do not contain water will not absorb microwaves and thus will not heat up.
Though some worry that standing next to a microwave oven can cause cancer, this is not the case, as the technology does not generate enough energy. Moreover, the metal mesh on the door of microwave ovens keeps the microwaves from spilling out, and microwave ovens have built-in safety devices that prevent them from working while the door is open.