The microwave, now a ubiquitous kitchen item, was invented in 1945 by the Raytheon Corporation, after an engineer realized that the magnetron tubes they were using to make radars could also produce heat. Like many important inventions, it was discovered by accident and became essential.
Old or faulty door seals are the most common causes of microwave radiation leakage. Mechanical abuse, a build-up of dirt, or simple wear and tear of continued use can cause door seals to be less effective. Theoretically, there will be small amounts of leakage through the viewing glass but measurements have shown this to be insignificant.
There have been allegations of radiation injury from microwave ovens, but none as a direct result of microwave exposure. The injuries known to FDA have been injuries that could have happened with any oven or cooking surface. For example, many people have been burned by the hot food, splattering grease, or steam from food cooked in a microwave oven.
Although heat is produced directly in the food, microwave ovens do not cook food from the "inside out." When thick foods are cooked, the outer layers are heated and cooked primarily by microwaves while the inside is cooked mainly by the conduction of heat from the hot outer layers.
This why baked potatoes work so well in a microwave, or why food cooks better when it's covered by a paper towel or a punctured plastic sheet. Much like the microwave oven itself, the skin of a baked potatoe, for example, absorbs the radiation which is then trapped within its skin, cooking the meat of the potato.
However, the microwave oven has well known limitations. It can’t produce a crispy brown crust on foods like a conventional oven can, for example. Also, because they can heat things so quickly, food sometimes becomes overheated, and some items like potatoes can even explode, creating a mess. The same things are possible in ordinary ovens, but it is easier to make a mistake with a microwave oven because it happens so quickly.
The market for microwave ovens is mature in most industrialized nations. Penetration rates in households within industrialized countries are in the 95 percent range, meaning that new sales are generated primarily by replacement purchases, what are often referred to as distress purchases within the industry. In the United States many homes have more than one microwave and, as already mentioned, many workplaces provide microwave ovens for use in employee kitchens and lunchrooms.
By the turn of the century, the microwave had gone from being a new and exotic technological kitchen device to being a standard kitchen appliance found in most places where cooking took place. It had become a primary technology and was thus something to which others adapted their technologies.
Early microwave ovens were much larger than those we have today—about the size of a refrigerator. These were sold in limited numbers to restaurants. It was not until after about 1965, after Raytheon acquired Amana Refrigeration, Inc., that they became smaller and less expensive. By the mid-1970s they were selling in the millions.
After the war Raytheon began offering civilian products, the microwave being among the most famous. Raytheon engineer Percy Spencer discovered microwave cooking when, as he stood in front of an active magnetron, a candy bar in his pocket began to melt. Intrigued, he sent out for popcorn kernels – and they began to pop. With that, a new appliance was soon on its way.
. In microwave cooking, the microwaves act on the water molecules in the food, causing them to vibrate. The vibration causes friction, which generates heat, thereby cooking the food...
Essentially, Microwaves turn electricty into electromagnetic radiation, and distributes that radiation evenly inside the microwave chamber. The radiation causes food molecules to vibrate, and thus heat up. Regular ovens heat up the air and walls around the food as well as the food itself. Microwaves only act on the food itself.
A microwave oven is an appliance that cooks or warms up food using microwaves produced by an electronic vacuum tube called a magnetron. The magnetron converts electricity to electromagnetic radiation (the microwaves), which is made up of waves of electric and magnetic energy. Once generated by the magnetron, the microwaves travel through a metal enclosure called a waveguide to a stirrer fan, which distributes the microwaves into the cooking cavity...
Microwaves (short waves or high frequency radio waves) are the shortest of radio waves, with a length of 0.1 millimeter and a frequency of 3 x 109 Hz. They are found in the non-ionizing portion of the energy spectrum, between radio waves and visible light. "Non-ionizing" means that microwaves do not detach charged particles and produce atoms with an unbalanced plus or minus charge. Microwaves can therefore safely produce heat and not cause food to become radioactive.