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A microwave oven uses dielectric heating to cook food. Dielectric heating, also known as electronic heating, radio frequency heating, and high-frequency heating, is the process in which a radio frequency (RF) alternating electric field, or radio wave or microwave electromagnetic radiation heats a dielectric material.
A microwave oven does not pose this problem. 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.
Inside a microwave oven, there really do exist EM free-space microwaves, since the wavelength is far shorter than the gap between the metal walls. However, inside the metal plates of a dielectric heater, that isn't true, so the entire effect is near-field, without production or absorption of any genuine radio waves-- even if the frequences are ...
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Microwave and other radio frequencies cause heating, and this can cause burns or eye damage if delivered in high intensity, [38] or hyperthermia as with any powerful heat source. Microwave ovens use this form of radiation, and have shielding to prevent it from leaking out and unintentionally heating nearby objects or people.
Microwave ovens are not tuned to any specific resonant frequency for water molecules in the food. They cook food via dielectric heating of polar molecules, notably water and fats. Microwave ovens do not cook food from the inside out. 2.45 GHz microwaves can only penetrate approximately 1–1.5 inches (2.5–3.8 centimeters) into most foods.
A microwave oven passes microwave radiation at a frequency near 2.45 GHz (12 cm) 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 ...
In radio-frequency engineering and communications engineering, a waveguide is a hollow metal pipe used to carry radio waves. [1] This type of waveguide is used as a transmission line mostly at microwave frequencies, for such purposes as connecting microwave transmitters and receivers to their antennas, in equipment such as microwave ovens, radar sets, satellite communications, and microwave ...