Microwaves Dr inż. ZDZISŁAW PÓLKOWSKI Polkowice, 2015 University of Pitesti Dolnośląska Wyższa Szkoła Przedsiębiorczości i Techniki w Polkowicach Simedre Mirel-Adrian
What are microwaves? 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. Microwave radiation are the radiating wave movements in which microwave energy travels. The wavelengths can be from as long as one meter to as short as one millimeter. Microwaves have a frequency range of 0.3 Ghz to 300 Ghz. They are found between the radio waves and the infrared waves in the electromagnetic spectrum.
Where can we find them? Microwaves take a straight line path. They can pass through non- metal materials such as plastic and glass, but get reflected off metal surfaces. Microwaves are absorbed by materials that have a high water content and produce heat, some examples are food, fruits, vegetables etc. This is where the microwave kitchen appliances work, the microwave oven (in the picture) is used for heating up our food by microwaves.
Uses A microwave oven uses a magnetron microwave generator to produce microwaves at a frequency of approximately 2.45 GHz for the purpose of cooking food. Microwave ovens cook food by causing molecules of water and other compounds in the food to vibrate or rotate. The vibrations generate heat, which warms the food. Given that food contains moisture, it is easily cooked by this method. Microwaves pass easily through the Earth's atmosphere, penetrating clouds, smoke, and light rain and snow. For this reason, microwaves are used in broadcasting transmissions. For instance, microwaves are used in television news coverage, to transmit signals from a specially equipped van in a remote location to a television station. In addition, they are used for transmissions to and from satellites, and to take satellite images of the Earth.
The technology known as radar (an acronym for "radio detection and ranging") involves the use of microwave radiation to detect the range, speed, and other characteristics of remote objects. Wireless communications between various devices—such as computers, printers, digital cameras, and personal digital assistants (PDAs)—rely on microwaves, often in the 900 megahertz (MHz), 2.4 GHz, or 5.0 GHz bands. This type of short-range network is known as WLAN (Wireless Local Area Network). Large, wireless computer networks covering a university campus or city also communicate by microwave transmissions. The communications protocol (standard for data transfer) is known as a wireless MAN (Metropolitan Area Network) protocol, such as WiMAX (Worldwide Interoperability for Microwave Access). For commercial applications, these microwave communications are in the 2.5 GHz, 3.5 GHz and 5.8 GHz ranges.
Several mobile phone networks use the lower microwave frequencies. Microwaves are used to generate plasma for many semiconductor processing techniques, such as reactive ion etching and plasma- enhanced chemical vapor deposition (PECVD). A maser is a device in which atoms or molecules are stimulated to amplify and emit a highly focused, coherent beam of microwave radiation. The term maser is an acronym for "microwave amplification by stimulated emission of radiation." Masers are used in atomic clocks and as amplifiers in radio telescopes. Microwaves can theoretically be used for wireless power transmission through outer space and the atmosphere. In the 1970s and early 1980s, NASA worked 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.
Microwave ovens A microwave oven consists: a high voltage transformer, an electron tube called magnetron, a wave guide fan and a oven chamber. The transformer passes electric energy to the magnetron and the magnetron converts this electric energy into microwave radiation. The microwaves are reflected in the oven chamber and are absorbed by the food. The microwave oven could be one of the great inventions of the 20th century -- hundreds of millions of homes worldwide have one. Just think about how many times you use a microwave every day. You're running late for work, so there's no time to fix breakfast at home. On your way to the office, you stop to gas up your car. Inside the quickie-mart, you grab a frozen breakfast burrito and pop it in the microwave on the counter. As you can see, microwave ovens are popular because they cook food in an amazingly short amount of time.
Concerns about microwaves Concerns about microwaves turning food radioactive are baseless. The radiation in microwave refers to the way in which microwaves move, not radioactivity. Microwaves are of a non-ionizing character. They do not have the energy to cause chemical changes in substances as would happen in the case of radioactivity. The danger of microwaves is that body tissue can be affected in the same way that food is. Microwaves can cause burns, eye cataracts and other injuries. It however, would take high levels of microwaves for this to happen. The levels of microwave radiation in kitchen appliances are very low.
How it works? If the microwaves are absorbed by an object, the warming effect will appear on the object. If the food absorb microwave radiation, to heat and cook food in a short time. This process is used in a microwave oven. radar is used to locate and determine the trace of an object with microwaves with a frequency of about Hz. Microwave with a wavelength between 1 millimeter to 1 meter. Or has frequency between 300 MHz (0.3 GHz) up to 300GHz.
Magnetron located in the microwave oven emits microwaves in a microwave oven. Then it spread to the region of maturation through an open gap at the top of the oven Reflected the microwave walls made of metal and are absorbed by food water molecules If a molecule is exposed to microwaves, microwave energy is absorbed by the molecules so that food can be cooked in a short time with the help of a propeller microwave molecules move faster vibrations caused friction, which causes heat used to cook food spread through direct radiation from the heat source to the food being cooked and raw food to be cooked Substances which will also absorb heat from the microwave is sugar, salt and fat.
James Clerk Maxwell Born: June 13, 1831, Ediburgh Died: November 5, 1879, Cambridge Book: A Dinamycal Theory of Electromanetic Field Nationality: British, Scottish Recognized by some people as the father of modern physics, James Clerk Maxwell was a very influential figure in the field of electricity, thermodynamics, photography, nuclear energy, and others. Invention of the electromagnetic spectrum that affect the development of television, radio, the microwave, and help in the development of radio and infrared. In the 15 th years old, he was able to present scientific paper work. Maxwell considered the greatest the teoritical physics in the entire period between Newton and Einstein. Maxwel is a scientist who has been tracing the link between symptoms of electricity and magnecity based on the knowledge that already exists at the time
James Clerk Maxwell, using his famous "Maxwell's equations," predicted the existence of invisible electromagnetic waves, of which microwaves are a part, in In 1888,Heinrich Hertz became the first to demonstrate the existence of such waves by building an apparatus that produced and detected microwaves in the ultra high frequency region. Hertz recognized that the results of his experiment validated Maxwell's prediction, but he did not see any practical applications for these invisible waves. Later work by others led to the invention of wireless communications, based on microwaves. Contributors to this work included Nikola Tesla, Guglielmo Marconi, Samuel Morse, SirWilliam Thomson (later Lord Kelvin), Oliver Heaviside, Lord Rayleigh, and Oliver Lodge.
Subdivisions of microwave frequencies icrowave signals are often divided into three categories: ultra high frequency (UHF) (0.3-3 GHz); super high frequency (SHF) (3-30 GHz); and extremely high frequency (EHF) ( GHz). In addition, microwave frequency bands are designated by specific letters. The designations by the Radio Society of Great Britain are given below.
Is Microwave Cooking Bad for You? [Microwave Radiation] Microwave cooking is a hot debate. Some believe that microwaves may cause cancer and other diseases. Yet it is the fastest, easiest and cleanest way to heat food and bake or grill, which is perfect for young and working adults. So true or false – radiation from microwave cooking negatively affects food and its surroundings? We ditch the myths and confirm the facts on microwaving food. Is microwave cooking bad for you? More specifically, is radiation from a microwave harmful? It is true that microwaves work on radiation, but hold on. The story continues… radiation is energy that travels in waves. But there are different waves – radio waves, X-ray and energy waves and micro wave is weaker than gamma rays. So don’t worry about turning into mutants. Conclusion: Microwave cooking is not harmful as long as the door is closed. Thankfully no microwave allows use unless the door is firmly secure.myths
Does microwave cooking and heating affect food? Microwave cooking and heating does not change the components of your food, it only heats the food. There is no evidence of toxin formation in food or carcinogens. If you over cook your food, then you are changing the components of the nutrients in your food. Over cooking on a grill, in the oven or micro wave - irrespective of the heat's source - destroys the nutrients. Conclusion: Microwaves do not change the nutrients of the food. Radiation leaks from the microwave Microwave leaks are possible if the door is damaged and cannot be shut properly. There are a few steps to ensure that your cooking machine does not leak of radiation. Do not fidget with the door Check for door damage regularly Clean the interior of the microwave frequently There are no serious microwave health risks unless it’s carelessness on your part. Be wise: Use the right containers, avoid cling film from touching the food, and maintain the microwave regularly.
Conclusion Microwave is an electromagnetic wave which length of wave is between 1mm – 1m, and wave frequency is between 300MHz- 300GHz The invention of microwave is based on the inventor of electromagnetic wave, he is James Clerk Maxwell. Application of microwave in daily life can be found in GPS, RADAR, and Microwave Oven Microwave radiation can be produce from a component names magnetron The important thing in microwave oven are magnetron, waveguide and strirer.