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Encyclopedia > Microwave

Microwaves are electromagnetic waves with wavelengths shorter than one meter and longer than one millimeter, or frequencies between 300 megahertz and 300 gigahertz. (UHF, SHF, EHF) Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... For other uses, see Wavelength (disambiguation). ... Ultra high frequency (UHF) designates a range (band) of electromagnetic waves whose frequency is between 300 MHz and 3. ... Microwave Slang for small waves, like at a beach, often used by surfers. ... EHF is a TLA that may stand for: Extremely High Frequency (audio or radio) Electrical hull fitting Episcopal Homes Foundation (ehf. ...


Apparatus and techniques may be described as "microwave" when the wavelengths of signals are roughly the same as the dimensions of the equipment, so that lumped-element circuit theory is inaccurate. As a consequence, practical microwave technique tends to move away from the discrete resistors, capacitors, and inductors used with lower frequency radio waves. Instead, distributed circuit elements and transmission-line theory are more useful methods for design, analysis, and construction of microwave circuits. Open-wire and coaxial transmission lines give way to waveguides, and lumped-element tuned circuits are replaced by cavity resonators or resonant lines. The lumped element model of electronic circuits makes the simplifying assumption that each element is an infinitesimal point in space, and that the wires connecting elements are perfect conductors. ... Resistor symbols (non-European) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ... See Capacitor (component) for a discussion of specific types. ... An inductor is a passive electrical device employed in electrical circuits for its property of inductance. ... Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ... Look up waveguide in Wiktionary, the free dictionary. ...


Effects of reflection, polarization, scattering, and atmospheric absorption usually associated with visible light are of practical significance in the study of microwave propagation. The same equations of electromagnetic theory apply at all frequencies. For thermodynamic relations, see Maxwell relations. ...


The name suggests a micrometer wavelength. However, the boundaries between far infrared light, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study. The term microwave generally refers to "alternating current signals with frequencies between 300 MHz (3×108 Hz) and 300 GHz (3×1011 Hz)."[1] (UHF, SHF, EHF) However, both IEC standard 60050 and IEEE standard 100 define "microwave" frequencies starting at 1 GHz (30 cm wavelength). For other uses, see Infrared (disambiguation). ... Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz, are in the region of the electromagnetic spectrum between 300 gigahertz (3x1011 Hz) and 3 terahertz (3x1012 Hz), corresponding to the wavelength range starting at submillimeter (<1 millimeter... “UHF” redirects here. ... Surface waves in water This article is about waves in the most general scientific sense. ... Ultra high frequency (UHF) designates a range (band) of electromagnetic waves whose frequency is between 300 MHz and 3. ... Microwave Slang for small waves, like at a beach, often used by surfers. ... EHF is a TLA that may stand for: Extremely High Frequency (audio or radio) Electrical hull fitting Episcopal Homes Foundation (ehf. ...


Electromagnetic waves longer (lower frequency) than microwaves are called "radio waves". Electromagnetic radiation with shorter wavelengths may be called "millimeter waves", terahertz radiation or even T-rays. Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz, are in the region of the electromagnetic spectrum between 300 gigahertz (3x1011 Hz) and 3 terahertz (3x1012 Hz), corresponding to the wavelength range starting at submillimeter (<1 millimeter...

Contents

Discovery

The existence of electromagnetic waves, of which microwaves are part of the frequency spectrum, was predicted by James Clerk Maxwell in 1864 from his equations. In 1888, Heinrich Hertz was the first to demonstrate the existence of electromagnetic waves by building an apparatus that produced and detected microwaves in the UHF region. The design necessarily used horse-and-buggy materials, including a horse trough, a wrought iron point spark, Leyden jars, and a length of zinc gutter whose parabolic cross-section worked as a reflection antenna. In 1894 J. C. Bose publicly demonstrated radio control of a bell using millimetre wavelengths, and conducted research into the propagation of microwaves. James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist from Edinburgh, Scotland, UK. His most significant achievement was aggregating a set of equations in electricity, magnetism and inductance — eponymously named Maxwells equations — including an important modification (extension) of the Ampères... For thermodynamic relations, see Maxwell relations. ... Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894) was the German physicist and mechanician for whom the hertz, an SI unit, is named. ... Original capacitor The Leyden jar was the original capacitor, invented in 1745 by Pieter van Muschenbroek (1700–1748) and used to conduct many early experiments in electricity. ... Sir Jagadish Chandra Bose (Bengali: জগদীশ চন্দ্র বসু Jôgdish Chôndro Boshu) (November 30, 1858 – November 23, 1937) was a Bengali physicist from undivided India, who pioneered the investigation of radio and microwave optics. ...

Plot of the zenith atmospheric transmission on the summit of Mauna Kea throughout the entire gigahertz range of the electromagnetic spectrum at a precipitable water vapor level of 0.001 mm. (simulated)

Download high resolution version (850x680, 20 KB)Plot of the zenith atmospheric transmission on the summit of Mauna Kea throughout the Gigahertz range at a precipitable water vapor level of 0. ... Download high resolution version (850x680, 20 KB)Plot of the zenith atmospheric transmission on the summit of Mauna Kea throughout the Gigahertz range at a precipitable water vapor level of 0. ... Mauna Kea is a dormant volcano in the Hawaiian Islands, one of five volcanic peaks that together form the island of Hawaii. ...

Frequency range

The microwave range includes ultra-high frequency (UHF) (0.3–3 GHz), super high frequency (SHF) (3–30 GHz), and extremely high frequency (EHF) (30–300 GHz) signals. This article is about the radio frequency. ... Microwave Slang for small waves, like at a beach, often used by surfers. ... Extremely high frequency is the highest radio frequency band. ...


Above 300 GHz, the absorption of electromagnetic radiation by Earth's atmosphere is so great that it is effectively opaque, until the atmosphere becomes transparent again in the so-called infrared and optical window frequency ranges In astronomy, the optical window is that portion of the electromagnetic spectrum that passes through the atmosphere all the way to the ground. ...


Microwave Sources

Vacuum tube based devices operate on the ballistic motion of electrons in a vacuum under the influence of controlling electric or magnetic fields, and include the magnetron, klystron, traveling wave tube (TWT), and gyrotron. These devices work in the density modulated mode, rather than the current modulated mode. This means that they work on the basis of clumps of electrons flying ballistically through them, rather than using a continuous stream. Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ... Reflex klystron Type 2K25 or 723 A/B. The threaded adjustment rod on the right side allows the position of the reflector to be adjusted (by compressing the reflex cavity), and thus the natural resonant frequency of the device. ... A traveling wave tube (TWT) is an electronic device used to produce high-power radio frequency signals. ... Gyrotrons are high powered electron tubes which emit a millimeter wave beam by bunching electrons with cyclotron motion in a strong magnetic field. ... For other uses, see Density (disambiguation). ...


A maser is a device similar to a laser, except that it works at microwave frequencies. A hydrogen radio frequency discharge, the first element inside a hydrogen maser (see description below) A maser is a device that produces coherent electromagnetic waves through amplification due to stimulated emission. ... For other uses, see Laser (disambiguation). ...


Uses

A microwave telecommunications tower on Wrights Hill in Wellington, New Zealand
A microwave telecommunications tower on Wrights Hill in Wellington, New Zealand
  • A microwave oven works by passing microwave radiation, usually at a frequency of 2450 MHz (a wavelength of 12.24 cm), through the food. Water, fat, and sugar molecules in the food absorb energy from the microwave beam in a process called dielectric heating. Many molecules (such as those of water) are electric dipoles, meaning that they have a positive charge at one end and a negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field induced by the microwave beam. This molecular movement creates heat as the rotating molecules hit other molecules and put them into motion. Microwave heating is most efficient on liquid water, and much less so on fats and sugars (which have less molecular dipole moment), and frozen water (where the molecules are not free to rotate). Microwave heating is sometimes incorrectly explained as a rotational resonance of water molecules: such resonance only occurs at much higher frequencies, in the tens of gigahertz. Moreover, large industrial/commercial microwave ovens operating in the 900 MHz range also heat water and food perfectly well.
    • A common misconception is that microwave ovens cook food from the "inside out". In reality, microwaves are absorbed in the outer layers of food in a manner somewhat similar to heat from other methods. The rays from a microwave electrically manipulate water particles to cook food. It is actually the friction caused by the movement that creates heat and warms the food. The misconception arises because microwaves penetrate dry nonconductive substances at the surfaces of many common foods, and thus often deposit initial heat more deeply than other methods. Depending on water content the depth of initial heat deposition may be several centimeters or more with microwave ovens, in contrast to grilling ("broiling" in American English), which relies on infrared radiation, or the thermal convection of a convection oven, which deposit heat shallowly at the food surface. Depth of penetration of microwaves is dependent on food composition and the frequency, with lower microwave frequencies being more penetrating.
  • Microwave radio is used in broadcasting and telecommunication transmissions because, due to their short wavelength, highly directive antennas are smaller and therefore more practical than they would be at longer wavelengths (lower frequencies). There is also more bandwidth in the microwave spectrum than in the rest of the radio spectrum; the usable bandwidth below 300 MHz is less than 300 MHz while many GHz can be used above 300 MHz. Typically, microwaves are used in television news to transmit a signal from a remote location to a television station from a specially equipped van.
  • Before the advent of fiber optic transmission, most long distance telephone calls were carried via microwave point-to-point links through sites like the AT&T Long Lines facility shown in the photograph. Starting in the early 1950's, frequency division multiplex was used to send up to 5,400 telephone channels on each microwave radio channel, with as many as ten radio channels combined into one antenna for the hop to the next site, up to 70 km away.
  • Radar also uses microwave radiation to detect the range, speed, and other characteristics of remote objects.
  • Wireless LAN protocols, such as Bluetooth and the IEEE 802.11 specifications, also use microwaves in the 2.4 GHz ISM band, although 802.11a uses ISM band and U-NII frequencies in the 5 GHz range. Licensed long-range (up to about 25 km) Wireless Internet Access services can be found in many countries (but not the USA) in the 3.5–4.0 GHz range.
  • Metropolitan Area Networks: MAN protocols, such as WiMAX (Worldwide Interoperability for Microwave Access) based in the IEEE 802.16 specification. The IEEE 802.16 specification was designed to operate between 2 to 11 GHz. The commercial implementations are in the 2.5 GHz, 3.5 GHz and 5.8 GHz ranges.
  • Wide Area Mobile Broadband Wireless Access: MBWA protocols based on standards specifications such as IEEE 802.20 or ATIS/ANSI HC-SDMA (e.g. iBurst) are designed to operate between 1.6 and 2.3 GHz to give mobility and in-building penetration characteristics similar to mobile phones but with vastly greater spectral efficiency.
  • Cable TV and Internet access on coax cable as well as broadcast television use some of the lower microwave frequencies. Some mobile phone networks, like GSM, also use the lower microwave frequencies.
  • Microwaves can be used to transmit power over long distances, and post-World War II research was done to examine possibilities. NASA worked in the 1970s and early 1980s to research the possibilities of using Solar power satellite (SPS) systems with large solar arrays that would beam power down to the Earth's surface via microwaves.

Image File history File links Metadata Size of this preview: 444 × 600 pixelsFull resolution (1665 × 2250 pixel, file size: 727 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Metadata Size of this preview: 444 × 600 pixelsFull resolution (1665 × 2250 pixel, file size: 727 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... For the first Duke of Wellington, see Arthur Wellesley, 1st Duke of Wellington. ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ... Radiation as used in physics, is energy in the form of waves or moving subatomic particles. ... For other uses, see Frequency (disambiguation). ... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... For other uses, see Wavelength (disambiguation). ... H2O and HOH redirect here. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ... This article is about sugar as food and as an important and widely traded commodity. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... Dielectric heating is the phenomenon in which radiowave or microwave electromagnetic radiation heats a dielectric material, especially as caused by Dipole rotation. There are two principal mechanisms by which a non-conductive material can be warmed in an EM field: Electrical conduction: current flow in the oscillating electric field allows... The Earths magnetic field, which is approximately a dipole. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... Dipole moment refers to the quality of a system to behave like a dipole. ... This article is about resonance in physics. ... Food cooking on a charcoal grill Grilling is a form of cooking that involves direct heat. ... Wikibooks Cookbook has more about this subject: Broiling Broiling is a process of cooking food with high heat with the heat applied directly to the food, most commonly from above. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... Convection is the internal movement of currents within fluids (i. ... Convection ovens use heated air that is forced into the oven by fans located in the back of the oven, generally for cooking food. ... Broadcasting is the distribution of audio and/or video signals which transmit programs to an audience. ... Copy of the original phone of Alexander Graham Bell at the Musée des Arts et Métiers in Paris Telecommunication is the assisted transmission of signals over a distance for the purpose of communication. ... Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a filter, a communication channel, or a signal spectrum, and is typically measured in hertz. ... Television news refers to the practice of disseminating current events via the media of television. ... Fiber Optic strands An optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light. ... Long distance in telecommunications, refers to telephone calls made outside a certain area, usually characterized by an area code outside of a local call area. ... This article does not adequately cite its references or sources. ... AT&T Long Lines logo, 1969-1983 The AT&T Long Lines microwave relay network provided long-distance transport services to AT&T and its customers from the late 1940s to the early 1980s. ... Frequency-division multiplexing (FDM) is a form of signal multiplexing where multiple baseband signals are modulated on different frequency carrier waves and added together to create a composite signal. ... For other uses, see Radar (disambiguation). ... The notebook is connected to the wireless access point using a PC card wireless card. ... For other senses of this word, see protocol. ... Bluetooth logo This article is about the electronic protocol named after Harald Bluetooth Gormson. ... The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ... IEEE 802. ... The industrial, scientific and medical (ISM) radio bands were originally reserved internationally for non-commercial use of RF electromagnetic fields for industrial, scientific and medical purposes. ... IEEE 802. ... The industrial, scientific and medical (ISM) radio bands were originally reserved internationally for non-commercial use of RF electromagnetic fields for industrial, scientific and medical purposes. ... The Unlicensed National Information Infrastructure (U-NII) radio band is part of the radio frequency spectrum used by IEEE-802. ... Metropolitan area networks, or MANs, are large computer networks usually spanning a city. ... Official WiMax logo WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. ... The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ... IEEE 802. ... Mobile Broadband is a type of wireless internet that differs from wifi, because it still relies on a bus card or USB device, instead of being built in. ... IEEE 802. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Cable television or Community Antenna Television (CATV) (and often shortened to cable) is a system of providing television, FM radio programming and other services to consumers via radio waves transmitted directly to people&#8217;s televisions through fixed coaxial cables as opposed to the over-the-air method used in... Terrestrial television (also known as over-the-air or OTA) is the traditional method of television broadcast signal delivery, by radio waves. ... The Global System for Mobile communications (GSM: originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world. ... Nasas Glenn Research Center clean room. ... A Plasma lamp In physics and chemistry, a plasma is an ionized gas, and is usually considered to be a distinct phase of matter. ... Reactive ion etching (RIE) is a technology using plasma to etch material deposited on wafers. ... DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ... This article does not cite any references or sources. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... This article is about the American space agency. ... An artists depiction of a solar satellite, which could send energy wirelessly to a space vessel or planetary surface. ... A photovoltaic module is composed of individual PV cells. ... The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ...

Microwave frequency bands

The microwave spectrum is usually defined as electromagnetic energy ranging from approximately 1 GHz to 1000 GHz in frequency, but older usage includes lower frequencies. Most common applications are within the 1 to 40 GHz range. Microwave Frequency Bands as defined by the Radio Society of Great Britain in the table below: This article lacks information on the importance of the subject matter. ...

Microwave frequency bands
Designation Frequency range
L band 1 to 2 GHz
S band 2 to 4 GHz
C band 4 to 8 GHz
X band 8 to 12 GHz
Ku band 12 to 18 GHz
K band 18 to 26.5 GHz
Ka band 26.5 to 40 GHz
Q band 30 to 50 GHz
U band 40 to 60 GHz
V band 50 to 75 GHz
E band 60 to 90 GHz
W band 75 to 110 GHz
F band 90 to 140 GHz
D band 110 to 170 GHz

The above table reflects Radio Society of Great Britain (RSGB) usage. The term P band is sometimes used for Ku Band. For other definitions see Letter Designations of Microwave Bands L band (20-cm radar long-band) is a portion of the microwave band of the electromagnetic spectrum ranging roughly from 0. ... The S band ranges from 2 to 4 GHz. ... C band (compromise band) is a portion of electromagnetic spectrum in the microwave range of frequencies ranging from 4 to 6 GHz. ... The X band (3-cm radar spot-band) of the microwave band of the electromagnetic spectrum roughly ranges from 5. ... The Ku band (kay-yoo kurz-under band) is a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 11 to 18 GHz. ... K band is a portion of the electromagnetic spectrum in the microwave range of frequencies ranging between 12 to 63 GHz. ... The Ka band (kurz-above band) is a portion of the K band of the microwave band of the electromagnetic spectrum. ... The V band (vee-band) of the electromagnetic spectrum ranges from 50 to 75 GHz. ... The E band is the range of radio frequencies from 2 GHz to 3 GHz in the electromagnetic spectrum. ... The W band of the microwave part of the electromagnetic spectrum and ranges from 75 to 111 GHz. ... The F band is the range of radio frequencies from 3 GHz to 4 GHz in the electromagnetic spectrum. ... The D band is the range of radio frequencies from 1 GHz to 2 GHz in the electromagnetic spectrum. ... This article lacks information on the importance of the subject matter. ...


Health effects

Microwaves contain insufficient energy to directly chemically change substances by ionization, and so are an example of nonionizing radiation. The word "radiation" refers to the fact that energy can radiate, and not to the different nature and effects of different kinds of energy. Electromagnetic radiation can be classified into ionizing radiation and non-ionizing radiation, based on whether it is capable of ionizing atoms and breaking chemical bonds. ... Non-ionizing radiation (or, esp. ...


The health effects of microwaves are controversial. A great number of studies have been undertaken in the last two decades, some concluding that microwaves pose a hazard to health, and others concluding they are safe. It is understood that microwave radiation of a level that causes heating of living tissue is hazardous (due to the possibility of overheating and burns) and most countries have standards limiting exposure, such as the Federal Communications Commission RF safety regulations. Still at issue is whether lower levels of microwave energy have bioeffects.


Synthetic reviews of literature indicate the predominance of their safety of use. [2] [3]


History and research

Perhaps the first, documented, formal use of the term microwave occurred in 1931:

"When trials with wavelengths as low as 18 cm were made known, there was undisguised surprise that the problem of the micro-wave had been solved so soon." Telegraph & Telephone Journal XVII. 179/1

Perhaps the first use of the word microwave in an astronomical context occurred in 1946 in an article "Microwave Radiation from the Sun and Moon" by Robert Dicke and Robert Beringer. Robert Henry Dicke (May 6, 1916 &#8211; March 4, 1997) was an American physicist and astrophysicist. ...


For some of the history in the development of electromagnetic theory applicable to modern microwave applications see the following figures:

Specific significant areas of research and work developing microwaves and their applications: “Ørsted” redirects here. ... Michael Faraday, FRS (September 22, 1791 – August 25, 1867) was an English chemist and physicist (or natural philosopher, in the terminology of that time) who contributed to the fields of electromagnetism and electrochemistry. ... James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist from Edinburgh, Scotland, UK. His most significant achievement was aggregating a set of equations in electricity, magnetism and inductance — eponymously named Maxwells equations — including an important modification (extension) of the Ampères... Heinrich Rudolf Hertz (February 22, 1857 - January 1, 1894) was the German physicist and mechanician for whom the hertz, an SI unit, is named. ... Nikola Tesla (1856-1943)[1] was a world-renowned Serbian inventor, physicist, mechanical engineer and electrical engineer. ... For the inventor of radio,and macoroni see the competing claims in history of radio and the invention of radio. ... Samuel Finley Breese Morse (April 27, 1791 – April 2, 1872) was an American painter of portraits and historic scenes, the creator of a single wire telegraph system, and co-inventor, with Alfred Vail, of the Morse Code. ... For other persons named William Thomson, see William Thomson (disambiguation). ... Oliver Heaviside (May 18, 1850 – February 3, 1925) was a self-taught English electrical engineer, mathematician, and physicist who adapted complex numbers to the study of electrical circuits, developed techniques for applying Laplace transforms to the solution of differential equations, reformulated Maxwells field equations in terms of electric and... See also Rayleigh fading Rayleigh scattering Rayleigh number Rayleigh waves Rayleigh-Jeans law External links Nobel website bio of Rayleigh About John William Strutt MacTutor biography of Lord Rayleigh Categories: People stubs | 1842 births | 1919 deaths | Nobel Prize in Physics winners | Peers | British physicists | Discoverer of a chemical element ... Vanity Fair cartoon. ... Jagdish Chandra Bose (November 30, 1858&#8211;November 23, 1937) was a leading physicist of his age. ...

Specific work on microwaves
Work carried out by Area of work
Barkhausen and Kurz Positive grid oscillators
Hull Smooth bore magnetron
Varian Brothers Velocity modulated electron beam → klystron tube
Randall and Boot Cavity magnetron

Barkhausen is also a locality in Detmold, see Detmold-Barkhausen Heinrich Georg Barkhausen (December 2, 1881 _ February 20, 1956), born at Bremen was a German physicist. ... Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ... A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ... Reflex klystron Type 2K25 or 723 A/B. The threaded adjustment rod on the right side allows the position of the reflector to be adjusted (by compressing the reflex cavity), and thus the natural resonant frequency of the device. ...

References

  1. ^ Pozar, David M. (1993). Microwave Engineering Addison-Wesley Publishing Company. ISBN 0-201-50418-9.
  2. ^ Dugauquier C. – Effects of exposure to electromagnetic fields (microwaves) on mammalian pregnancy. Litterature review – Médecine et Armées, 2006; 34 (3): 215-218
  3. ^ Heynick C. et al. – Radio Frequency Electromagnetic Fields: Cancer,Mutagenesis, and Genotoxicity – Bioelectromagnetics Supplement, 2003; 6:S74-S100 .

External links

See also

Radio spectrum
ELF SLF ULF VLF LF MF HF VHF UHF SHF EHF
3 Hz 30 Hz 300 Hz 3 kHz 30 kHz 300 kHz 3 MHz 30 MHz 300 MHz 3 GHz 30 GHz
30 Hz 300 Hz 3 kHz 30 kHz 300 kHz 3 MHz 30 MHz 300 MHz 3 GHz 30 GHz 300 GHz


“CMB” redirects here. ... In telecommunications, a diversity scheme refers to a method for improving the reliability of a message signal by utilizing two or more communication channels with different characteristics. ... Electron cyclotron resonance is a phenomenon observed both in plasma physics and condensed matter physics. ... Home appliances are electrical/mechanical appliances which accomplish some household functions, such as cooking or cleaning. ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Radiation as used in physics, is energy in the form of waves or moving subatomic particles. ... In satellite communications, rain fade refers to the absorption of a microwave Radio Frequency (RF) signal by rain or snow, and is especially prevalent in frequencies above 11 GHz. ... For the book by Sir Isaac Newton, see Opticks. ... Microwave chemistry is the science of applying microwave irradiation to chemical reactions . Microwaves act as high frequency electric fields and will generally heat anything with a mobile electric charge. ... This article or section does not cite its references or sources. ... This article does not cite any references or sources. ... Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ... Extremely low frequency (ELF) is the band of radio frequencies from 3 to 30 Hz. ... Super Low Frequency (SLF) is the frequency range between 30 hertz and 300 hertz. ... Ultra Low Frequency (ULF) is the frequency range between 300 hertz and 3000 hertz. ... Very low frequency or VLF refers to radio frequencies (RF) in the range of 3 to 30 kHz. ... Low Frequency or LF refers to Radio Frequencies (RF) in the range of 30–300 kHz. ... Medium frequency (MF) refers to radio frequencies (RF) in the range of 300 kHz to 3000 kHz. ... High frequency (HF) radio frequencies are between 3 and 30 MHz. ... Very high frequency (VHF) is the radio frequency range from 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m). ... This article is about the radio frequency. ... Microwave Slang for small waves, like at a beach, often used by surfers. ... Extremely high frequency is the highest radio frequency band. ...


  Results from FactBites:
 
Food Safety Education: Cook | Food Safety Facts - Microwave Oven (601 words)
Microwave ovens can play an important role at mealtime, but special care must be taken when cooking or reheating meat, poultry, fish, and eggs to make sure they are prepared safely.
When partially cooking food in the microwave oven to finish cooking on the grill or in a conventional oven, it is important to transfer the microwaved food to the other heat source immediately.
Microwave plastic wraps, wax paper, cooking bags, parchment paper, and white microwave-safe paper towels should be safe to use.
CDRH Consumer Information - Microwave Oven Radiation (1843 words)
Microwaves are a form of "electromagnetic" radiation; that is, they are waves of electrical and magnetic energy moving together through space.
Microwaves have three characteristics that allow them to be used in cooking: they are reflected by metal; they pass through glass, paper, plastic, and similar materials; and they are absorbed by foods.
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.
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