Sources of Microwaves
- Microwave Ovens. The most common source of microwaves is ovens used for cooking food. ...
- Police Radar Guns. Microwave radar guns employ the Doppler principle for measuring speed. ...
- Manufacturing. Another source of microwaves is manufacturing. ...
- Communications. ...
What are 5 uses of microwaves?
Microwaves are suitable for wireless transmission of signals having larger bandwidth. Microwaves are most commonly used in satellite communications, radar signals, phones, and navigational applications. Other applications where microwaves used are medical treatments, drying materials, and in households for the preparation of food.
What are the best cheap microwaves?
Pros:
- Named one of the best compact microwaves by Top Ten Reviews.
- Slightly more powerful and spacious than our top choice for best value, the Toshiba EM925A5A-SS, with 950 watts and a 1.1-cubic-foot interior.
- Heats and defrosts food well for a model this size, according to tests.
- 12.75-inch turntable can accommodate a mixing bowl or large dinner plate.
What is the cheapest microwave?
These are the best affordable countertop microwaves we tested:
- Magic Chef 1.1 Cubic-Foot Countertop
- Galanz ExpressWave
- GE 1.1 Cubic-Foot Mid-Size
- Hamilton Beach EM031M2ZC-X1
- Toshiba EM131A5C with Smart Sensor
- Toshiba EM925A5A
- Magic Chef MCM990ST 900W Countertop Oven with Stainless Steel Front
- Black+Decker EM925AB9 Digital
- LG NeoChef with Smart Inverter and EasyClean
- AmazonBasics Microwave
What are the natural sources of microwave radiation?
What Are Microwaves?
- Communications & radar. Microwaves are used mostly for point-to-point communications systems to convey all types of information, including voice, data and video in both analog and digital formats, according to ...
- Microwave heat sources. One of the most common uses of microwaves is to heat food quickly. ...
- Natural microwave sources. ...
When were microwaves invented?
Microwaves were first generated in the 1890s in some of the earliest radio experiments by physicists who thought of them as a form of "invisible light". James Clerk Maxwell in his 1873 theory of electromagnetism, now called Maxwell's equations, had predicted that a coupled electric field and magnetic field could travel through space as an electromagnetic wave, and proposed that light consisted of electromagnetic waves of short wavelength. In 1888, German physicist Heinrich Hertz was the first to demonstrate the existence of radio waves using a primitive spark gap radio transmitter. Hertz and the other early radio researchers were interested in exploring the similarities between radio waves and light waves, to test Maxwell's theory. They concentrated on producing short wavelength radio waves in the UHF and microwave ranges, with which they could duplicate classic optics experiments in their laboratories, using quasioptical components such as prisms and lenses made of paraffin, sulfur and pitch and wire diffraction gratings, to refract and diffract radio waves like light rays. Hertz produced waves up to 450 MHz; his directional 450 MHz transmitter consisted of a 26 cm brass rod dipole antenna with a spark gap between the ends, suspended at the focal line of a parabolic antenna made of a curved zinc sheet, powered by high voltage pulses from an induction coil. His historic experiments demonstrated that radio waves like light exhibited refraction, diffraction, polarization, interference and standing waves, proving that radio waves and light waves were both forms of Maxwell's electromagnetic waves .
How are microwaves used in telecommunications?
Microwaves are especially suitable for this use since they are more easily focused into narrower beams than radio waves, allowing frequency reuse; their comparatively higher frequencies allow broad bandwidth and high data transmission rates, and antenna sizes are smaller than at lower frequencies because antenna size is inversely proportional to the transmitted frequency. Microwaves are used in spacecraft communication, and much of the world's data, TV, and telephone communications are transmitted long distances by microwaves between ground stations and communications satellites. Microwaves are also employed in microwave ovens and in radar technology.
What is the wavelength of a microwave?
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively.
How are microwaves used in space?
Microwaves are used in spacecraft communication , and much of the world's data, TV, and telephone communications are transmitted long distances by microwaves between ground stations and communications satellites. Microwaves are also employed in microwave ovens and in radar technology.
How far can a microwave travel?
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).
How do microwaves work?
This means that they work on the basis of clumps of electrons flying ballistically through them, rather than using a continuous stream of electrons. Low-power microwave sources use solid-state devices such as the field-effect transistor (at least at lower frequencies), tunnel diodes, Gunn diodes, and IMPATT diodes.
What does the prefix "micro" mean?
The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range. Rather, it indicates that microwaves are "small" (having shorter wavelengths), compared to the radio waves used prior to microwave technology.
What is the spectrum of microwaves?
Microwaves are one frequency on the electromagnetic spectrum, which encompasses the frequency range of all electromagnetic radiation. At the center of the spectrum, you have visible, or optical, light. On one side of the spectrum, the side with higher frequencies, you have ionizing radiation. These waves have a lot of energy ...
How much radiation does a microwave emit?
The FDA regulates microwave oven radiation and has set that limit at 5mW of radiation per square centimeter throughout the device’s lifetime.
What is the use of microwaves in the military?
Microwaves are also used by the military. Right around World War II, it was noted that microwaves could detect the placement of solid objects by bouncing off them , and Radio Detection and Ranging (RADAR) technology was born. RADAR locates approaching ships, missiles, and aircraft through the use of microwaves.
Is microwave radiation safe?
Microwaves and other forms of non-ionizing radiation are generally regarded as safe, but there is mounting evidence that, in fact, that may not be the case. Technically, microwaves are a form of radiofrequency (RF) radiation.
Can microwaves leak out?
Even though manufacturers take measures to contain the radiation produced by the device, it is still possible that some will leak out. Microwaves are also used by the military.
Can you stand directly next to a microwave?
With microwave radiation, the inverse-square rule applies: the closer to the source of radiation, the greater your exposure levels. Regularly standing directly next to your microwave oven while it cooks, for example, puts you at greater risk of experiencing health issues than standing ten feet away from it. We can safely say that microwaves can be ...
Is a microwave a kitchen appliance?
When you hear the word microwave, the popular kitchen appliance may spring to mind. In actuality, however, this term encompasses much more than that. Microwaves are all around us, produced naturally by the cosmos as well as from manmade sources. Just as there are concerns associated with microwave ovens, however, ...
Why are microwaves used?
Microwave heat sources. One of the most common uses of microwaves is to heat food quickly. Microwave ovens are possible because microwaves can be used to transmit thermal energy. The discovery of this phenomenon was purely accidental.
What type of radiation is microwave?
Microwaves are a type of electromagnetic radiation, as are radio waves, ultraviolet radiation, X-rays and gamma-rays. Microwaves have a range of applications, including communications, radar and, perhaps best known by most people, cooking. Electromagnetic radiation is transmitted in waves or particles at different wavelengths and frequencies.
What is the microwave background?
What Are Microwaves? This image unveiled March 21, 2013, shows the cosmic microwave background (CMB) as observed by the European Space Agency's Planck space observatory. The CMB is a snapshot of the oldest light in our Universe, imprinted on the sky when the Universe was just 380 000 years old.
What spectrum is microwave?
Microwaves fall in the range of the EM spectrum between radio and infrared light. The electromagnetic spectrum, from highest to lowest frequency waves. (Image credit: Shutterstock) Microwaves have frequencies ranging from about 1 billion cycles per second, or 1 gigahertz (GHz), up to about 300 gigahertz and wavelengths of about 30 centimeters ...
What is the most famous observation of extraterrestrial microwaves?
However, perhaps the most famous observation of extraterrestrial microwaves was conducted by two Bell Labs scientists working on a telecommunications system using a large ground-based horn antenna.
What is the purpose of microwaves?
Microwaves are used mostly for point-to-point communications systems to convey all types of information, including voice, data and video in both analog and digital formats , according to the Federal Communications Commission (FCC). They are also used for supervisory control and data acquisition (SCADA) for remote machinery, switches, valves and signals.
How many regions are there in the electromagnetic spectrum?
This broad range of wavelengths is known as the electromagnetic spectrum EM spectrum). The spectrum is generally divided into seven regions in order of decreasing wavelength and increasing energy and frequency.
When was microwave technology first used?
When microwave technology was first used to develop radar systems in World War 2 , no one could ever have imagined that it would go on to have so many amazing uses in the post-war era. Today microwaves power nearly everything around us.
What is microwave communication?
3. Cell Phone Communication. Microwaves are used as a medium for transmitting information between mobile devices. When you send a message, voice call, a video clip, or a photo, this information is transformed into signals which are then sent through microwaves to the nearest cell tower.
Why use microwave radiation for drones?
One of the benefits of using microwave radiation to eliminate drone threats is that it isn’t dependent on weather conditions, or any other visibility inhibitors. As long as the HPM is powered on, it will keep sending out blasts of microwaves to neutralize any drones in its path.
What is a microwave oven called?
Oh, how the Stone Age man would have loved the convenience modern-day microwaves ovens have to offer. It’s no coincidence though that they are called “microwaves ” after all, they use microwave technology to heat your food.
Why are microwaves used in medical?
Microwaves are now being widely used in numerous medical applications. Some of these include: Microwaves cause heating. This property has been harnessed to create targeted dielectric thermal desiccation of human tissue.
Why do satellite dishes need to be made of metal?
The satellite dish also needs to be made of metal since metallic surfaces help to reflect microwaves too. 3. Cell Phone Communication.
Why is Wi-Fi the same as microwave?
They operate on the same frequency bands of the electromagnetic spectrum. Wi-Fi is short for wireless fidelity and refers to the ability of Wi-Fi microwaves to operate at different frequencies.
What is the purpose of microwaves?
Microwaves are the principal carriers of high-speed data transmissions between stations on Earth and also between ground-based stations and satellites and space probes. A system of synchronous satellites about 36,000 km above Earth is used for international broadband of all kinds of communications—e.g., television and telephone.
What is a microwave receiver?
Microwave transmitters and receivers are parabolic dish antennas. They produce microwave beams whose spreading angle is proportional to the ratio of the wavelength of the constituent waves to the diameter of the dish. The beams can thus be directed like a searchlight. Radar beams consist of short pulses of microwaves.
How is infrared radiation absorbed?
Infrared radiation is absorbed and emitted by the rotations and vibrations of chemically bonded atoms or groups of atoms and thus by many kinds of materials. For instance, window glass that is transparent to visible light absorbs infrared radiation by the vibration of its constituent atoms.
What is the wavelength of a microwave?
Microwaves. The microwave region extends from 1,000 to 300,000 MHz (or 30 cm to 1 mm wavelength). Although microwaves were first produced and studied in 1886 by Hertz, their practical application had to await the invention of suitable generators, such as the klystron and magnetron. Microwaves are the principal carriers of high-speed data ...
How does a microwave oven work?
Microwaves play an increasingly wide role in heating and cooking food. They are absorbed by water and fat in foodstuffs (e.g., in the tissue of meats) and produce heat from the inside.
Why is microwave radar important?
Microwave radar is therefore widely used for guiding airplanes and vessels and for detecting speeding motorists. Microwaves can penetrate clouds of smoke but are scattered by water droplets, so they are used for mapping meteorologic disturbances and in weather forecasting.
Does microwave cooking reduce cooking time?
In most cases, this reduces the cooking time a hundredfold. Such dry objects as glass and ceramics, on the other hand, are not heated in the process, and metal foils are not penetrated at all. The heating effect of microwaves destroys living tissue when the temperature of the tissue exceeds 43° C (109° F).
What are the sources of microwaves?
Man-made sources of microwaves include microwave ovens, masers, circuits, communication transmission towers, and radar. Either solid state devices or special vacuum tubes may be used to produce microwaves.
What is microwave radiation?
Microwave radiation is a type of electromagnetic radiation. The prefix "micro-" in microwaves doesn't mean microwaves have micrometer wavelengths, but rather that microwaves have very small wavelengths compared with traditional radio waves (1 mm to 100,000 km wavelengths). In the electromagnetic spectrum, microwaves fall between infrared radiation ...
How far can a microwave travel?
While lower frequency radio waves can follow the contours of the Earth and bounce off layers in the atmosphere, microwaves only travel line-of-sight, typically limited to 30-40 miles on the Earth's surface. Another important property of microwave radiation is that it's absorbed by moisture. A phenomenon called rain fade occurs at the high end ...
Why is microwave radiation called radiation?
Microwave radiation is called " radiation " because it radiates outward and not because it's either radioactive or ionizing in nature. Low levels of microwave radiation are not known to produce adverse health effects. However, some studies indicate long-term exposure may act as a carcinogen.
Why do microwaves burn?
This is caused by thermal expansion within the inner ear. Microwave burns can occur in deeper tissue—not just on the surface—because microwaves are more readily absorbed by tissue that contains a lot of water. However, lower levels of exposure produce heat without burns.
Can microwaves cause cataracts?
Microwave exposure can cause cataracts, as dielectric heating denatures proteins in the eye's lens, turning it milky. While all tissues are susceptible to heating, the eye is particularly vulnerable because it doesn't have blood vessels to modulate temperature.
Overview
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. 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-frequency enginee…
Propagation
Microwaves travel solely by line-of-sight paths; unlike lower frequency radio waves, they do not travel as ground waves which follow the contour of the Earth, or reflect off the ionosphere (skywaves). Although at the low end of the band they can pass through building walls enough for useful reception, usually rights of way cleared to the first Fresnel zone are required. Therefore, on the surface …
Antennas
The short wavelengths of microwaves allow omnidirectional antennas for portable devices to be made very small, from 1 to 20 centimeters long, so microwave frequencies are widely used for wireless devices such as cell phones, cordless phones, and wireless LANs (Wi-Fi) access for laptops, and Bluetooth earphones. Antennas used include short whip antennas, rubber ducky antennas, sleeve dipo…
Design and analysis
The term microwave also has a more technical meaning in electromagnetics and circuit theory. Apparatus and techniques may be described qualitatively as "microwave" when the wavelengths of signals are roughly the same as the dimensions of the circuit, so that lumped-element circuit theory is inaccurate, and instead distributed circuit elements and transmission-line theory are more useful methods for design and analysis.
Microwave sources
High-power microwave sources use specialized vacuum tubes to generate microwaves. These devices operate on different principles from low-frequency vacuum tubes, using the ballistic motion of electrons in a vacuum under the influence of controlling electric or magnetic fields, and include the magnetron (used in microwave ovens), klystron, traveling-wave tube (TWT), and gyrotron. Th…
Microwave uses
Microwave technology is extensively used for point-to-point telecommunications (i.e. non-broadcast uses). Microwaves are especially suitable for this use since they are more easily focused into narrower beams than radio waves, allowing frequency reuse; their comparatively higher frequencies allow broad bandwidth and high data transmission rates, and antenna sizes are smaller than at lower …
Microwave frequency bands
Bands of frequencies in the microwave spectrum are designated by letters. Unfortunately, there are several incompatible band designation systems, and even within a system the frequency ranges corresponding to some of the letters vary somewhat between different application fields. The letter system had its origin in World War 2 in a top secret U.S. classification of bands used in radar sets; this is the origin of the oldest letter system, the IEEE radar bands. One set of microwa…
Microwave frequency measurement
Microwave frequency can be measured by either electronic or mechanical techniques.
Frequency counters or high frequency heterodyne systems can be used. Here the unknown frequency is compared with harmonics of a known lower frequency by use of a low-frequency generator, a harmonic generator and a mixer. The accu…