How the microwave oven was made from WWII radar tech

sometimes, weapons and other projects pushed by the urgency of war have been converted into civilian technology. such is the casing of nuclear power plants, the internet, but besides radar technical school, which inexpectedly and unwittingly led to the invention of the microwave oven — one of the most wide used home appliance in the world .

Radar and microwaves

Before and throughout the war, British ground radar technology was rather well matched by German scientific advances. Here, mid-war ground radar station FuMO 214 Würzburg-Riese [US National Archives]
In 1920, a young physicist called Albert Hull, who worked at the General Electric Research Laboratory in Schenectady, New York, invented the magnetron pipe — a coaxial cylindrical anode and cathode with an axial magnetic field produced by an external coil. It was a magnet that controlled electrical current inside an evacuate electron tube, or vacuum tube. Hull believed the magnetron would be successful as an electrical converter, but 20 years later it would prove most useful in telecommunications. During WWII, the british were looking to devise a higher-frequency radar engineering for the war effort. A radar locates distant objects by bouncing radio waves off of them and then analyzing the reflections. Locating the enemy from afar was crucial to the war effort .
Engineers planned to build a new radar system based on electromagnetic waves in the microwave region of the radio spectrum. Such a system would require smaller antenna and detect smaller objects than lower-frequency, longer-wavelength radars. Microwaves correspond to a region in the EM spectrum defined by having wavelengths between approximately 1 meter and 1 millimeter, corresponding to frequencies between 300 MHz ( Mega = 106 Hz = 106 sec-1 ) and 300 GHz ( Giga = 109 Hz ). today, microwaves are frequently used to transmit data from satellites in space to radio dishes on earth, but rear then building a high-octane reservoir of microwave radiation proved to be a challenge.

ad In 1940, John Turton Randall and Harry Boot, two young physicists working in England at the University of Birmingham, found a manner to modify Hull ’ s original magnetron metro to make it produce microwaves with high gear adequate baron. The improved invention was called a cavity magnetron tube, and curtly after its foremost test runs it became the heart of the Allies ’ advanced radar systems that were so substantive — possibly critical — to the overall Allied victory in World War II .

From spotting Luftwaffe fighters to popcorn

During the war, one of the leading suppliers of cavity magnetron tube was the Massachusetts-based Raytheon Manufacturing Company. Working there was a self-taught engineer by the identify of Percy Spencer. One day, in 1946, while testing a modern magnetron unit, Spencer felt a foreign tickling sensation and on the spur of the moment noticed that the sugarcoat barroom in his pocket had melted. He then placed popcorn, eggs, and early foods in front of the device and they all cooked — actually the egg exploded all over his friend ’ sulfur confront !

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Leave this field empty if you’re human: soon after the accidental discovery, engineers at Raytheon went to work on Spencer ’ s new theme, developing and refining it to be of hardheaded habit. A class later, the beginning commercial product hit the market. After a few decades of agitation, myths and legends regarding microwave function, public demand began to swell with acceptance until the sales of microwave ovens finally surpassed those of gas ranges in 1975. Furthermore, in 1976 the microwave became a more common family appliance than the dishwasher as it found its home in about fifty-two million U.S. households, or 60 % of U.S. homes at the time. adIntroduced in 1967, the Amana Radarange microwave oven would forever change the way American families prepare meals. Image: SMECC
Although microwave ovens today have advanced since the very first designs, at their core they still use the lapp cavity magnetron tube that was harnessed therefore effectively for WWII radar .

How a microwave oven works

Inside the Magnetron: Large magnets impose a field that causes the outward-flowing cloud to revolve (left). As it does, it forms spokes that pass each cavity between the plates (right). A passing spoke provides negative charge to the cavity, which then falls off until the next spoke arrives. The rise and fall creates an electromagnetic field in the cavities that oscillates at 2.45 gigahertz. Image: GEORGE RETSECK
The microwave oven is quite a feat of physics and engineering. At its kernel, the oven exploits the polarity of body of water molecules which tend to rotate themselves into alignment with their cocksure ends in the management of an electric field. With each rotation, the water atom ’ s electrostatic electric potential energy is transferred into thermal energy. An analogy would be a identical crowd room, in which everyone is told to turn and face the stagecoach. In doing so, people brush up against one another as they turn and friction causes the conversion of some of their energy into thermal energy. The magnetron reverses its electric field very flying, so water molecules flip second and away at a rate of billions of times per second.

Magnetron High voltage is sent to the cathode filament. After it heats up, it emits electrons that the positively charged anode plates attract. The attached antenna resonates at 2.45 gigahertz and emits microwaves from its tip--just like a radio-transmission antenna. Image: GEORGE RETSECK
This hotness is what actually cooks food in the oven. Because all particles in the food are vibrating and generating heat at the same prison term, food cooked in the microwave cooks much more swiftly than food cooked in a conventional oven where heating system must lento travel from the outside coat of the food inward. The lapp radio waves that cook your food pass harmlessly through plastics, glaze, and ceramics. It is this characteristic that keeps credit card plates from melting and glasses from exploding. It is besides this feature of microwaves that makes them sol energy efficient ; they heat only the food and nothing more .
As you might have learned from experience ( ouch ! ), metals reflect microwaves which is why they credit line the walls of the microwave such that no waves elude and cook anyone in the kitchen !