Query: Sending oscillating microwaves from an antenna inside a vacuum through an electromagnetic field through a dielectric material, such as water, creates radio frequency heating at the molecular level

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Electromagnetic radiation <=SEP=> In physics , electromagnetic radiation ( EM radiation or EMR ) refers to the waves ( or their quanta , photons ) of the electromagnetic field , propagating ( radiating ) through space carrying electromagnetic radiant energy . It includes radio waves , microwaves , infrared , ( visible ) light , ultraviolet , X - , and gamma radiation .   Classically , electromagnetic radiation consists of electromagnetic waves , which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light through a vacuum . The oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation , forming a transverse wave . The wavefront of electromagnetic waves emitted from a point source ( such as a lightbulb ) is a sphere . The position of an electromagnetic wave within the electromagnetic spectrum could be characterized by either its frequency of oscillation or its wavelength . The electromagnetic spectrum includes , in order of increasing frequency and decreasing wavelength : radio waves , microwaves , infrared radiation , visible light , ultraviolet radiation , X-rays and gamma rays .   Electromagnetic waves are produced whenever charged particles are accelerated , and these waves can subsequently interact with other charged particles . EM waves carry energy , momentum and angular momentum away from their source particle and can impart those quantities to matter with which they interact . Quanta of EM waves are called photons , whose rest mass is zero , but whose energy , or equivalent total ( relativistic ) mass , is not zero so they are still affected by gravity . Electromagnetic radiation is associated with those EM waves that are free to propagate themselves ( `` radiate '' ) without the continuing influence of the moving charges that produced them , because they have achieved sufficient distance from those charges . Thus , EMR is sometimes referred to as the far field . In this language , the near field refers to EM fields near the charges and current that directly produced them , specifically , electromagnetic induction and electrostatic induction phenomena .   In the quantum theory of electromagnetism , EMR consists of photons , the elementary particles responsible for all electromagnetic interactions . Quantum effects provide additional sources of EMR , such as the transition of electrons to lower energy levels in an atom and black-body radiation . The energy of an individual photon is quantized and is greater for photons of higher frequency . This relationship is given by Planck 's equation E = hν , where E is the energy per photon , ν is the frequency of the photon , and h is Planck 's constant . A single gamma ray photon , for example , might carry ~ 100,000 times the energy of a single photon of visible light .   The effects of EMR upon chemical compounds and biological organisms depend both upon the radiation 's power and its frequency . EMR of visible or lower frequencies ( i.e. , visible light , infrared , microwaves , and radio waves ) is called non-ionizing radiation , because its photons do not individually have enough energy to ionize atoms or molecules . The effects of these radiations on chemical systems and living tissue are caused primarily by heating effects from the combined energy transfer of many photons . In contrast , high ultraviolet , X-rays and gamma rays are called ionizing radiation since individual photons of such high frequency have enough energy to ionize molecules or break chemical bonds . These radiations have the ability to cause chemical reactions and damage living cells beyond that resulting from simple heating , and can be a health hazard .

Microwave oven <=SEP=> A microwave oven ( commonly referred to as a microwave ) is a kitchen appliance that heats and cooks food by exposing it to microwave radiation in the electromagnetic spectrum . 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 of a homogeneous , high water content food item ; food is more evenly heated throughout ( except in heterogeneous , dense objects ) than generally occurs in other cooking techniques .   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 . The countertop microwave oven was first introduced in 1967 by the Amana Corporation , and their use has spread into commercial and residential kitchens around the world .   Microwave ovens are popular for reheating previously cooked foods and cooking a variety of foods . They are also useful for rapid heating of otherwise slowly prepared cooking items , such as hot butter , fats , and chocolate . Unlike conventional ovens , microwave ovens usually do not directly brown or caramelize food , since they rarely attain the necessary temperatures to produce Maillard reactions . Exceptions occur in rare cases where the oven is used to heat frying-oil and other very oily items ( such as bacon ) , which attain far higher temperatures than that of boiling water . Microwave ovens have a limited role in professional cooking , because the boiling-range temperatures produced in especially hydrous foods impede flavors produced by the higher temperatures of frying , browning , or baking . However , additional heat sources can be added to microwave ovens , or into combination microwave ovens , to produce these other heating effects , and microwave heating may cut the overall time needed to prepare such dishes . Some modern microwave ovens are part of over-the-range units with built-in extractor hoods .

Dielectric heating <=SEP=> Dielectric heating , also known as electronic heating , RF ( radio frequency ) heating , and high-frequency heating , is the process in which a high-frequency alternating electric field , or radio wave or microwave electromagnetic radiation heats a dielectric material . At higher frequencies , this heating is caused by molecular dipole rotation within the dielectric .   RF dielectric heating at intermediate frequencies , due to its greater penetration over microwave heating , shows greater promise than microwave systems as a method of very rapidly heating and uniformly preparing certain food items , and also killing parasites and pests in certain harvested crops .

Microwave <=SEP=> Microwaves are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter ; with frequencies between 300 MHz and 300 GHz . Different sources define different frequency ranges as microwaves ; the above broad definition includes both UHF and EHF ( millimeter wave ) bands . A more common definition in radio engineering is the range between 1 and 100 GHz ( 300 and 3 mm ) . In all cases , microwaves include the entire SHF band ( 3 to 30 GHz , or 10 to 1 cm ) at minimum . Frequencies in the microwave range are often referred to by their IEEE radar band designations : S , C , X , Ku , K , or Ka band , or by similar NATO or EU designations .   The prefix in microwave is not meant to suggest a wavelength in the micrometer range . It indicates that microwaves are `` small '' , compared to the radio waves used prior to microwave technology , in that they have shorter wavelengths . The boundaries between far infrared , terahertz radiation , microwaves , and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study .   Microwaves travel by line-of-sight ; unlike lower frequency radio waves they do not diffract around hills , follow the earth 's surface as ground waves , or reflect from the ionosphere , so terrestrial microwave communication links are limited by the visual horizon to about 40 miles ( 64 km ) . At the high end of the band they are absorbed by gases in the atmosphere , limiting practical communication distances to around a kilometer . Microwaves are extremely widely used in modern technology . They are used for point-to-point communication links , wireless networks , microwave radio relay networks , radar , satellite and spacecraft communication , medical diathermy and cancer treatment , remote sensing , radio astronomy , particle accelerators , spectroscopy , industrial heating , collision avoidance systems , garage door openers and keyless entry systems , and for cooking food in microwave ovens .