Questions tagged [microwaves]

Microwaves, broadly defined, are electromagnetic radiation with wavelengths ranging from one meter to one millimeter; or with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm). This range includes both UHF and EHF (millimeter waves) and the entire SHF band (3 to 30 GHz, or 10 to 1 cm).

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Need the (frequency dependent) dielectric permitivity of quartz

I have desperately googled to find a table or a graph for the complex dielectric permitivity of quartz (e.g. fused quartz), as a function of frequency, at room temperature. I am mostly interested in ...
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In a ion source, how do we make the ions get out of the cavity?

Ion sources are devices that allow creating ion beams (e.g. argon ions) and to project them outside the device, for example to be further processed by a particle accelerator, or to irradiate materials ...
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If we have a cosmic microwave background should't we also have a cosmic radio wave background?

I'm a layman in physics, but here is what I understand: What we see in the sky with naked eyes is a map of electromagnetic waves in the frequency visible to the human vision. But that kind of ...
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Coupling ion ray with a EM wave and penetration depth

Ion sources are devices that allow creating ion beams (e.g. argon ions) and to project them outside the device, for example to be further processed by a particle accelerator, or to irradiate materials ...
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Relation between Radiance and Surface power density (i.e poynting vector intensity)

I am attending a microwave remote sensing course and I have same problem to understand the relation between the radiance and the intensity of poynting's vector. The radiance is defined as: $L(\theta,\...
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Do microwaves only make water spin? Can microwaves spin single atoms?

I’ve been reading how microwave ovens cook food by spinning water molecules and was wondering if water is the only molecule that can be spun using microwaves, possibly by raising or lowering the ...
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Does microwaves nevertheless pass through smaller slits?

It is known that the Foucault currents prevent the microwaves to leave a microwave oven (MWO). The waves can not pass tru several times smaller openings than their wavelength because the grid of the ...
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What would happen on an atomic level to mercury in a microwave?

I'm not sure why I was thinking of this, but I did and I couldn't think of an equivalent physical model to relate microwaved liquid Mercury to. Polar substances are heated by dielectric heating, the ...
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Microwave turntable absorption

I have heard that microwave turntables absorb microwaves when there is very little load in the cavity, which limits the reflection to the magnetron. Will this also limit the leakage radiation from the ...
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Why wire grid polarizers do not re emit absorbed radiation both ways?

The wikipedia page on polarizers states about wire grid polarizers that : "Electromagnetic waves that have a component of their electric fields aligned parallel to the wires will induce the ...
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Frequency upconversion of pulses shorter than 1 IF period

I have a rather elementary frequency upconversion/mixer question, perhaps so simple that it does not warrant a real question but rather just a reference to a website/tutorial (that I have not been ...
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Is water thermolysis via microwave heating feasible?

Can water molecules be heated enough (2500°C? 3000°C?) to be separated into hydrogen and oxygen by thermolysis via a microwave emitter? I've searched around but it appears this hasn't been researched? ...
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Why do microwave ovens need to have a resonant cavity?

Why is it considered necessary for the microwave oven to be a resonant cavity? If it wasn't resonant then the energy wouldn't have anywhere to go but in the food as well. So I don't understand the ...
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Is the accuracy of atomic clocks about engineering limits?

I read that a microwave with specific wavelength is shone on a bunch of atom to make them change energy state from ground to excited state, then they measure this difference in energy to determine its ...
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Microwave inside-out cooking true/false

The wikipedia article on microwave ovens says Another misconception is that microwave ovens cook food "from the inside out", meaning from the center of the entire mass of food outwards. It ...
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How can effect of electromagnetic radiation on human sperm be explained physically? [closed]

I am not sure if this question belongs here. If it doesn't belong here, feel free to remove it (and maybe tell me where to post this instead?). I have been researching the question of whether ...
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Why is my bluetooth signal able to exit my microwave?

I was shopping for a bluetooth meat thermometer. Since this device would also be used in my combo (conventional and microwave) oven, which is shielded for microwaves, I expected the device to not work....
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What implies that transverse EM fields satisfy Laplace's in TEM waves?

I am reading Pozar's Microwave engieering. When explaining the TEM waves (pag98 4th edition) he defines $\bar{e}(x, y)$ as the transverse electric field. He proves that $$\nabla_{t}^{2} \bar{e}(x, y)=...
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If I made a double slit using microwave oven door, do I get an interference pattern?

Imagine the following setup: A microwave oven door with 2 holes big enough for the wavelength of microwave to pass through, high power magnetron as the source of microwave and wall of metal to produce ...
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Field at exactly the cutoff frequency of a waveguide

What happens below or above a cutoff frequency is very well documented! I have never seen though a clear explanation (as a matter of fact no explanation) about what happens at exactly the cutoff ...
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Can lenses and mirrors be described in terms of beamwidth and directivity?

As a first background, I am an Electrical Engineer with experience in antennae design for microwave bands. Lately, I have been interested by optical devices, and I notice one strange phenomenon: when ...
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How to experimentally orient the rotation axis in the Bloch sphere during Rabi oscillations?

Rabi oscillations are well known in the field of quantum physics. I have seen plots of experimental realizations of Rabi oscillations. However, I do not understand how to manipulate the rotation axis ...
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When an electrical field is generated inside a Faraday cage (say as in a microwave) does the cage act as a reflective surface to amplify the field?

I am familiar with the concept that electrical fields within a Faraday cage do not extend outside of the cage and that electrical fields generated outside do not extend into it. My question is -- when ...
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Building a "stelaser" - a star-powered maser network that distributes free global electricity. Why and Why not?

I wish to design a Space Based Power platform that delivers microwave power from space. This approach has been criticized (famously by Elon Musk), because converting sunlight to electrons to ...
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Why do microwaves penetrate flesh when visible light does not at the same intensity?

I understand why microwaves penetrate flesh, it has been answered before here, but in the most answers it was mentioned that although microwaves have less energy per photon when compared to visible ...
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Scattering parameter oscillation

Why does scattering parameter $S_{11}$ for a two port measurement with a simple cable oscillate with frequency?
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Microwave effect

I'm new to the forum. I state that I am a technician and I have to deal every day, even with various types of radar, but I am not only concerned with this. I found out on the web about the danger of ...
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Determining the frequency of a monochromatic light source from measurements of irradiance alone?

Let's say we have a monochromatic source of unknown frequency (say, a laser) and some device/sensor that measures the total photon energy absorbed over a fixed time interval (essentially, irradiance). ...
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Is it okay to sleep with the wifi router next to me?

Where I sleep I have my wifi router right above me. I don't know if this is safe for my health since it emits radiation. Some people say that it should be safe since the radiation emitted is non-...
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Transmission coefficient in microwave cavities

I have a trouble finding the transmission coefficient S in the given case below. I am an undergraduate student and this is an exercise handed to me by my supervisor, which I haven't yet to get around ...
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Why does piercing plastic film lid before microwaving help?

I've done this many times: buy food in a plastic box covered by a very thin plastic film. The instructions say simply: stab the film with a fork, several times microwave it eat it I was very ...
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Why does canola oil heat up in the microwave?

Introduction: I read on Wikipedia's list of common misconceptions that microwaves work not by emitting the resonant frequency of water, but as a result of dielectric heating. As I understand it, this ...
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Why do airbags activate when subjected to microwave energy?

I remember watching a few years ago, a show on YouTube called "Is It A Good Idea To Microwave This?" The presenters regularly placed everyday items in a microwave and observed what happened. ...
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If Photons do not have 'charge,' how do microwaves which use the negative and positive polarity of the wave agitate $\rm H_2O$?

As far as i have understood it, Photons do not have Charge. Charge as i have understood it is the Positive and Negative charge of an atom. In context to $\rm H_2O$ being a polar molecule, microwaves ...
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How does a microwave steamer work?

While I am no physicist, I am convinced this is a physics question: How does a microwave steamer work? It seems like a scam to me. Wouldn't the microwave be cooking the food and heating the water at ...
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Do slits cause light to become coherent?

In the young double slit experiment, you have a single slit followed by two slits. I believe it is the single slit which cause the light to diffract and become coherent and the double slit is to ...
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Multiple frequencies microwave heating

I was wondering how to calculate the power dissipation density (electromagnetic losses) when two waves of different frequencies are used simultaneously to heat a dielectric object. Of course, this ...
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Why do electromagnetic waves hate discontinuities?

It's known (and it's the basis of many designs of microwave devices) that electromagnetic wave propagation in a medium occurs in a good way (i.e. without reflection and higher order modes excited), if ...
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Microwave heater for heatin graphite crucible

I'm interested in melting alumina in a graphite crucible, some details here. As a tungsten heating wire apparently will oxidize rather quickly in a regular atmosphere, i was wondering if i can't heat ...
34 votes
4 answers
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Stood in front of microwave with the door open [closed]

I was cooking something in the microwave and opened the door early to check on it and the microwave didn't stop. I didn't realize this for a few seconds and when I did I shut the microwave off but I'm ...
19 votes
7 answers
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In a microwave oven, why do smaller portions heat up faster?

Sorry for brevity, but what is the exact physics explanation of why smaller quantities placed inside a microwave oven heat up faster than when you place a larger quantity of a similar material inside?
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Why does the left cup’s top region till where the water is filled the most hot point and not the points below?

So I have two cups here. Black cup on the left and a white cup on the right.The region where I have made a dark red horizontal line is the region till where the water is filled.The left one is made ...
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In a rectangular waveguide, how can one determine if any propagation modes exist?

I'm currently studying microwave engineering, and I came across the query mentioned above. I know that rectangular waveguides use TE(m,n),TE and TM modes, but I do not understand how these modes came ...
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Why the fields of the quasi-TEM mode of microstrip line tend to concentrate in the dielectric as frequency goes higher?

A microstrip line is a waveguiding structure as shown below: Because of the inhomogeneity, the fundamental mode of propagation is a quasi-TEM mode, which means that the z components of the E and H ...
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When a microwave oven stops, why are unpopped kernels very hot and popped kernels not hot?

A commonplace empirical observation is that when a microwave oven stops, unpopped kernels are very hot (it's physically painful to touch them) and popped kernels are not. Is there an elementary (or ...
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How to explain mobile phone rings inside microwave oven? [duplicate]

So finally tested myself and found: mobile phone rings inside microwave oven. Microwave oven frequency is 2.5 GHz which gives wavelength of 12 centimeters. Cellular network waves are even longer. Thay ...
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Why dont microwaves pass through the microwave door [duplicate]

What is the classical explanation for why the microwaves won't pass through the microwave door? I know the microwaves behave like particles and dont pass through the microwave door but I am asking why ...
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Microwaves: why do they cook food?

I have looked up several explanations of microwaves and how they work but I am unclear on a few key parts of how they actually make the food hotter. How I understand it now: In addition to the light ...
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Why does chocolate burn if you microwave it with milk?

Chocolate Science! I melt 3 spoons of dark chocolate in microwave oven in low. It melts in 3 minutes and it's just mildly warm. I add half a spoon of milk which makes it a bit cold again. So I ...
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Do metals have negative permittivity (real part) at microwave frequencies?

I have been studying metamaterials from Electromagnetic Metamaterials: Transmission line theory and microwave applications by Caloz and Itoh. They have commented that metals at optical frequencies ...
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