Inventions Of Microwave Oven

The microwave oven was invented by Percy LeBaron Spencar, who was one of a number of wartime radar scientists to notice the heating effect of microwaves. Other dismissed the phenomenon, but Spencer used it to revolutionize cooking practices.
Percy LeBaron Spencer (USA) is said to have discovered the culinary potential of microwaves after finding a melted chocolate and peanut bar in his pocket - he had just walked past a microwave-emitting device called a magnetron, and decided to investigate whether that is what had melted the chocolate bar. The cavity magnetron had been developed in the early 1940's by physicists Sir John Randall and Dr H.A.H Boot (both England) as a means of producing microwaves for use in airborne radar, and their invention was patented in 1947. This new radar technology was shared with wartime ally the USA, where President Roosevelt, well aware of the tactical importance of the cavity magnetron, described it as "the most valuable cargo ever to reach our shores".

Spencar, working for the Raytheon Manufacturing Co. in Newton, Massachusetts, suggested various improvements to the device, and Raytheon duly won the contract to manufacture magnetrons. Noticing the heating effect of the microwave beam, which is now known to be due to the excitation of molecules rather than the radiation of heat, Spencer investigated further. He put a bag of maize in the path of the microwave beam and seconds later he had a bag of popcorn. Then he created the world's first microwave oven by cutting a hole in the side of a kettle and directing the microwave beam from the magnetron through the hole. An egg placed in the kettle cooked so quickly that it exploded in spectacular fashion, and this demonstration was enough to convince Raytheon to begin work on developing Spencer's invention.

On 8 October 1945 Spencer filed a patent for a "method of treating foodstuffs" (granted 1950), and the first prototype microwave oven was installed , in a restaurant in Boston, USA, the following year. The prototype was a success, and Raytheon produced its first commercial microwave ovens in 1947, known as the Raydarange.

Source - The Book Of Invention by Ian Harrison