Instruct: Given a question, retrieve passages that can help answer the question.
Query: How much did the first microwave oven cost?
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.
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.
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.
On 8 May 2012, he appeared on the Radio Four series "The Life Scientific", talking to Jim al-Khalili about the Gaia hypothesis. On the program, he mentioned how his ideas had been received by various people, including Jonathan Porritt. He also mentioned how he had a claim for inventing the microwave oven. He later explained this claim in an interview with "The Manchester Magazine". Lovelock said that he did create an instrument during his time studying causes of damage to living cells and tissue, which had, according to him, "almost everything you would expect in an ordinary microwave oven". He invented the instrument for the purpose of heating up frozen hamsters in a way that caused less suffering to the animals, as opposed to the traditional way which involved putting red hot spoons on the animals' chest to heat them up. He believes that at the time, nobody had gone that far and made an embodiment of an actual microwave oven. However, he does not claim to have been the first person to have the idea of using microwaves for cooking.
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]
Any form of cooking will destroy some nutrients in food, but the key variables are how much water is used in the cooking, how long the food is cooked, and at what temperature.[44] Nutrients are primarily lost by leaching into cooking water, which tends to make microwave cooking healthier, given the shorter cooking times it requires.[45] Like other heating methods, microwaving converts vitamin B12 from an active to inactive form; the amount of conversion depends on the temperature reached, as well as the cooking time. Boiled food reaches a maximum of 100°C (212°F) (the boiling point of water), whereas microwaved food can get locally hotter than this, leading to faster breakdown of vitamin B12. The higher rate of loss is partially offset by the shorter cooking times required.[46]
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]
Microwave ovens have limited roles in professional cooking,[2] because the boiling-range temperatures of a microwave will not produce the flavorful chemical reactions that frying, browning, or baking at a higher temperature will. However, additional heat sources can be added to microwave ovens.
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.
Raytheon filed a patent on October 8, 1945 for a microwave cooking oven, eventually named the Radarange. In 1947, the first commercially produced microwave oven was about 6 feet tall, weighed about 750 lbs, and cost about 5,000 US$. In 1967 the first relatively affordable ($495) and reasonably sized (counter-top) microwave oven was available for sale.
A microwave oven (also commonly referred to as a microwave) is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range[1]. This induces polar molecules in the food to rotate and produce thermal energy in a process known as dielectric heating. Microwave ovens heat foods quickly and efficiently because excitation is fairly uniform in the outer 25–38 mm (1–1.5 inches) of a homogeneous, high water content food item; food is more evenly heated throughout than generally occurs in other cooking techniques.
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. 
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).
Compared to liquid water, microwave heating is less efficient on fats and sugars (which have a smaller molecular dipole moment).[31] Sugars and triglycerides (fats and oils) absorb microwaves due to the dipole moments of their hydroxyl groups or ester groups. However, due to the lower specific heat capacity of fats and oils and their higher vaporization temperature, they often attain much higher temperatures inside microwave ovens.[30] This can induce temperatures in oil or very fatty foods like bacon far above the boiling point of water, and high enough to induce some browning reactions, much in the manner of conventional broiling (UK: grilling), braising, or deep fat frying. Foods high in water content and with little oil rarely exceed the boiling temperature of water.
The radiation produced by a microwave oven is non-ionizing. It therefore does not have the cancer risks associated with ionizing radiation such as X-rays and high-energy particles. Long-term rodent studies to assess cancer risk have so far failed to identify any carcinogenicity from 2.45 GHz microwave radiation even with chronic exposure levels (i.e. large fraction of life span) far larger than humans are likely to encounter from any leaking ovens.[64][65] However, with the oven door open, the radiation may cause damage by heating. Every microwave oven sold has a protective interlock so that it cannot be run when the door is open or improperly latched.
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]
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.
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.
Starting in the 1970s, Adair conducted physiology studies as a fellow at the John B. Pierce Laboratory in New Haven to learn how humans and animals react to heat. This work led her to focus on the controversial area of microwaves and their effect on human health. Experimenting first on squirrel monkeys and then on human volunteers, she concluded that microwave radiation from microwave ovens, cells phones, and power lines is harmless to humans and animals.
The microwave frequencies used in microwave ovens are chosen based on regulatory and cost constraints. The first is that they should be in one of the industrial, scientific, and medical (ISM) frequency bands set aside for unlicensed purposes. For household purposes, 2.45GHz has the advantage over 915MHz in that 915MHz is only an ISM band in the ITU Region 2 while 2.45GHz is available worldwide. Three additional ISM bands exist in the microwave frequencies, but are not used for microwave cooking. Two of them are centered on 5.8GHz and 24.125GHz, but are not used for microwave cooking because of the very high cost of power generation at these frequencies. The third, centered on 433.92MHz, is a narrow band that would require expensive equipment to generate sufficient power without creating interference outside the band, and is only available in some countries.
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.
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.
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]
Microwave heating, as distinct from RF heating, is a sub-category of dielectric heating at frequencies above 100 MHz, where an electromagnetic wave can be launched from a small dimension emitter and guided through space to the target. Modern microwave ovens make use of electromagnetic waves with electric fields of much higher frequency and shorter wavelength than RF heaters. Typical domestic microwave ovens operate at 2.45 GHz, but 915 MHz ovens also exist. This means that the wavelengths employed in microwave heating are 0.1 cm to 10 cm. This provides for highly efficient, but less penetrative, dielectric heating.