Instruct: Given a question, retrieve relevant documents that can help answer the question.
Query: What company first sold the microwave oven?
In 1947, Raytheon built the "Radarange", the first commercially available microwave oven.[13] It was almost 1.8 metres (5ft 11in) tall, weighed 340 kilograms (750lb) and cost about US$5,000 ($56,000 in 2018 dollars) each. It consumed 3 kilowatts, about three times as much as today's microwave ovens, and was water-cooled. The name was the winning entry in an employee contest.[14] An early Radarange was installed (and remains) in the galley of the nuclear-powered passenger/cargo ship NS Savannah. An early commercial model introduced in 1954 consumed 1.6 kilowatts and sold for US$2,000 to US$3,000 ($19,000 to $28,000 in 2018 dollars). Raytheon licensed its technology to the Tappan Stove company of Mansfield, Ohio in 1952.[15] They tried to market a large 220 volt wall unit as a home microwave oven in 1955 for a price of US$1,295 ($12,000 in 2018 dollars), but it did not sell well.
Raytheon's research on the magnetron tube revealed the potential of microwaves to cook food. In 1945, Raytheon's Percy Spencer invented the microwave oven by discovering that the magnetron could rapidly heat food. In 1947, the company demonstrated the Radarange microwave oven for commercial use.
Uneven heating in microwaved food can be partly due to the uneven distribution of microwave energy inside the oven, and partly due to the different rates of energy absorption in different parts of the food. The first problem is reduced by a stirrer, a type of fan that reflects microwave energy to different parts of the oven as it rotates, or by a turntable or carousel that turns the food; turntables, however, may still leave spots, such as the center of the oven, which receive uneven energy distribution. The location of dead spots and hot spots in a microwave can be mapped out by placing a damp piece of thermal paper in the oven. When the water saturated paper is subjected to the microwave radiation it becomes hot enough to cause the dye to be released which will provide a visual representation of the microwaves. If multiple layers of paper are constructed in the oven with a sufficient distance between them a three-dimensional map can be created. Many store receipts are printed on thermal paper which allows this to be easily done at home.[40]
In 1998 Parkes telescope began detecting fast radio bursts and related signals named perytons. At the time it was theorised that these might have been signals from another galaxy, emissions from neutron stars becoming black holes, or interference from lightning strikes. In 2015 it was determined that perytons were caused by staff members opening the door of the facility's microwave oven during its cycle. When the microwave oven door was opened, 1.4 GHz microwaves from the magnetron shutdown phase were able to escape. ″Subsequent tests revealed that a peryton can be generated at 1.4 GHz when a microwave oven door is opened prematurely and the telescope is at an appropriate relative angle″. ″It is still not clear if microwave ovens can be blamed for all instances of peryton reception″.
Lutefisk sold in North America may also be cooked in a microwave oven. The average cooking time is 8–10 minutes per whole fish (a package of two fish sides) at high power in a covered glass cooking dish, preferably made of heat resistant glass. The cooking time will vary, depending upon the power of the microwave oven.
In the 1960s, Litton bought Studebaker's Franklin Manufacturing assets, which had been manufacturing magnetrons and building and selling microwave ovens similar to the Radarange. Litton then developed a new configuration of the microwave: the short, wide shape that is now common. The magnetron feed was also unique. This resulted in an oven that could survive a no-load condition: an empty microwave oven where there is nothing to absorb the microwaves. The new oven was shown at a trade show in Chicago, and helped begin a rapid growth of the market for home microwave ovens. Sales volume of 40,000 units for the U.S. industry in 1970 grew to one million by 1975. Market penetration was faster in Japan, due to a re-engineered magnetron allowing for less expensive units. Several other companies joined in the market, and for a time most systems were built by defense contractors, who were most familiar with the magnetron. Litton was particularly well known in the restaurant business.
A microwave oven cooks or heats food by dielectric heating. Cooking food with microwaves was discovered by Percy Spencer on October 8, 1945, while building magnetrons for radar sets at Raytheon. Spencer was working on an active radar set when he noticed a strange sensation, and saw that a peanut candy bar he had in his pocket started to melt. Although he was not the first to notice this phenomenon, as the holder of 120 patents, Spencer was no stranger to discovery and experiment, and realized what was happening. The radar had melted his candy bar with microwaves. The first food to be deliberately cooked with microwaves was popcorn, and the second was an egg. In 1947, Raytheon under Percy Spencer demonstrated the world's first microwave oven built at the company which was called the "Radarange".
A variant of the conventional microwave is the convection microwave. A convection microwave oven is a combination of a standard microwave and a convection oven. It allows food to be cooked quickly, yet come out browned or crisped, as from a convection oven. Convection microwaves are more expensive than conventional microwave ovens. Some convection microwaves—those with exposed heating elements—can produce smoke and burning odors as food spatter from earlier microwave-only use is burned off the heating elements.
The first microwave oven injury was reported in 1973. Two women operated a microwave oven in a department store snack bar. After several years, the oven showed a malfunction manifesting by burning the food. The first woman noticed burning sensations in her fingers and very little pain or tenderness when nearby to the operating oven. A small lesion appeared on her left index finger, near the base of the fingernail. In the next four weeks, three fingers of her right hand became affected as well. Transverse ridging and deformations close to the nail base appeared on her fingernails. After five months since the initial symptoms, she visited a doctor; the examination found no abnormalities other than the nails. Topical steroid cream used over six weeks led to gradual improvement. The second woman experienced nail deformation at the same time as the first one, with the same clinical findings. The oven was returned to the manufacturer before the involvement of the doctor, and the amount of leakage could not be assessed.
Japan's Sharp Corporation began manufacturing microwave ovens in 1961. Between 1964 and 1966, Sharp introduced the first microwave oven with a turntable, a feature that promotes convenient even heating of food.[16] In 1965, Raytheon acquired Amana. In 1967, they introduced the first popular home model, the countertop Radarange, at a price of US$495 ($4,000 in 2018 dollars).
Microwave ovens heat food without getting hot themselves. Taking a pot off a stove, unless it is an induction cooktop, leaves a potentially dangerous heating element or trivet that will stay hot for some time. Likewise, when taking a casserole out of a conventional oven, one's arms are exposed to the very hot walls of the oven. A microwave oven does not pose this problem.
An example of investment-specific technological progress is the microwave oven. The idea of the microwave came to be by accident: in 1946 an engineer noticed that a candy bar in his pocket had melted while working on something completely unrelated to cooking (Gallawa 2005). The development of this good, from melting the candy bar to the home appliance we know today, took time and the investment of resources to make a microwave small and cheap. The first microwave oven cost between 2000 and 3000 dollars and was housed in refrigerator-sized cabinets (Gallawa 2005)! Today, almost any college student can enjoy a 3-minute microwaveable meal in the smallest dorm room. But a microwave's uses do not stop at the dorm room. Many industries have found microwave heating advantageous: it has been used to dry cork, ceramics, paper, leather, and so on (Gallawa 2005). However, for either college students or firms to reap the benefits of quick warming, they must first "invest" in a microwave oven (that "embodies" the technological advance). To realize the benefits of investment-specific technological progress you must first invest in a technology that embodies it.
Household microwave ovens have shielding around the inside of the oven that prevents microwaves from leaking out, as well as safety interlocks that prevent the oven from operating when the door is open. Therefore, burns due to direct exposure to microwave energy (as opposed to touching hot food) should not occur under normal circumstances.
There are also convection microwave ovens which combine a convection oven with a microwave oven to cook food with the speed of a microwave oven and the browning ability of a convection oven. 
Balmuda has since introduced several more small appliances, including a toaster, a microwave oven, an electric kettle, and a rice cooker, with Balmuda providing product design and distribution but all manufacturing outsourced to other companies. The toaster oven, called "The Toaster" and introduced in 2015, was not initially advertised to consumers, but sold so quickly that customers had to wait three months to get their product. The company has also developed a signature food product, BALMUDA The Curry, intended to be prepared with Balmuda appliances.
Direct microwave exposure is not generally possible, as microwaves emitted by the source in a microwave oven are confined in the oven by the material out of which the oven is constructed. Furthermore, ovens are equipped with redundant safety interlocks, which remove power from the magnetron if the door is opened. This safety mechanism is required by United States federal regulations.[60] Tests have shown confinement of the microwaves in commercially available ovens to be so nearly universal as to make routine testing unnecessary.[61] According to the United States Food and Drug Administration's Center for Devices and Radiological Health, a U.S. Federal Standard limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts of microwave radiation per square centimeter at approximately 5 cm (2in) from the surface of the oven.[62] This is far below the exposure level currently considered to be harmful to human health.[63]
Food and cookware taken out of a microwave oven are rarely much hotter than 100°C (212°F). Cookware used in a microwave oven is often much cooler than the food because the cookware is transparent to microwaves; the microwaves heat the food directly and the cookware is indirectly heated by the food. Food and cookware from a conventional oven, on the other hand, are the same temperature as the rest of the oven; a typical cooking temperature is 180°C (356°F). That means that conventional stoves and ovens can cause more serious burns.
From the late 1970s, Japanese companies such as Sharp Corporation manufactured low-cost microwave ovens that were affordable for residential use, leading to the rapid expansion of the microwave oven market in the 1980s. After Japanese dominance for much of the 1980s, with Sharp as market leader, South Korean manufacturers began entering the market in the late 1980s, with Samsung becoming a major microwave manufacturer.[18]
More recently, ovens have become slightly more high-tech in terms of cooking strategy. The microwave as a cooking tool was discovered by Percy Spencer in 1946, and with the help from engineers, the microwave oven was patented. The microwave oven uses microwave radiation to excite the molecules in food causing friction, thus producing heat.In cooking, the conventional oven is a kitchen appliance used for roasting and heating. Foods normally cooked in this manner include meat, casseroles and baked goods such as bread, cake and other desserts. In modern times, the oven is used to cook and heat food in many households across the globe.
A microwave oven passes microwave radiation at a frequency near  through food, causing dielectric heating primarily by absorption of the energy in water. Microwave ovens became common kitchen appliances in Western countries in the late 1970s, following the development of less expensive cavity magnetrons. Water in the liquid state possesses many molecular interactions that broaden the absorption peak. In the vapor phase, isolated water molecules absorb at around 22 GHz, almost ten times the frequency of the microwave oven.
Formerly found only in large industrial applications, microwave ovens increasingly became a standard fixture of residential kitchens in developed countries. By 1986, roughly 25% of households in the U.S. owned a microwave oven, up from only about 1% in 1971;[19] the U.S. Bureau of Labor Statistics reported that over 90% of American households owned a microwave oven in 1997.[19][20] In Australia, a 2008 market research study found that 95% of kitchens contained a microwave oven and that 83% of them were used daily.[21] In Canada, fewer than 5% of households had a microwave oven in 1979, but more than 88% of households owned one by 1998.[22] In France, 40% of households owned a microwave oven in 1994, but that number had increased to 65% by 2004.[23]
The development of the cavity magnetron in the UK made possible the production of electromagnetic waves of a small enough wavelength (microwaves). American engineer Percy Spencer is generally credited with inventing the modern microwave oven after World War II from radar technology developed during the war. Named the "Radarange", it was first sold in 1946. Raytheon later licensed its patents for a home-use microwave oven that was first introduced by Tappan in 1955, but these units were still too large and expensive for general home use. Sharp Corporation introduced the first microwave oven with a turntable between 1964 and 1966. The countertop microwave oven was first introduced in 1967 by the Amana Corporation. After Sharp introduced low-cost microwave ovens affordable for residential use in the late 1970s, their use spread into commercial and residential kitchens around the world. In addition to their use in cooking food, types of microwave ovens are used for heating in many industrial processes.
A microwave oven heats food by passing microwave radiation through it. Microwaves are a form of non-ionizing electromagnetic radiation with a frequency higher than ordinary radio waves but lower than infrared light. Microwave ovens use frequencies in one of the ISM (industrial, scientific, medical) bands, which are reserved for this use, so they do not interfere with other vital radio services. Consumer ovens usually use 2.45 gigahertz (GHz)— It is a wavelength of 12.2 centimetres (4.80in)—while large industrial/commercial ovens often use 915 megahertz (MHz)—32.8 centimetres (12.9in).[26] Water, fat, and other substances in the food absorb energy from the microwaves in a process called dielectric heating. Many molecules (such as those of water) are electric dipoles, meaning that they have a partial positive charge at one end and a partial negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field of the microwaves. Rotating molecules hit other molecules and put them into motion, thus dispersing energy. This energy, dispersed as molecular rotations, vibrations and/or translations in solids and liquids raises the temperature of the food, in a process similar to heat transfer by contact with a hotter body[27] It is a common misconception that microwave ovens heat food by operating at a special resonance of water molecules in the food. As noted microwave ovens can operate at many frequencies.[28][29]
In 1955 Joseph McVicker tested a wallpaper cleaner in Cincinnati schools, eventually becoming known as the product Play-Doh. The same year the Tappan Stove Company created the first microwave oven made for commercial, home use. James Spangler invented the first commercially successful portable vacuum cleaner, which he sold to The Hoover Company.
It is possible for metal objects to be microwave-oven compatible, although experimentation by users is not encouraged. Microwaving an individual smooth metal object without pointed ends, for example, a spoon or shallow metal pan, usually does not produce sparking. Thick metal wire racks can be part of the interior design in microwave ovens (see illustration). In a similar way, the interior wall plates with perforating holes which allow light and air into the oven, and allow interior-viewing through the oven door, are all made of conductive metal formed in a safe shape.