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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Microwave oven efficiency and conservation of energy

Wikipedia says that microwave ovens can be around 50-64% efficient at converting electricity into microwaves. Where does the energy lost at this stage go? And how much of the energy that is ...
Karl's user avatar
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How to practically generate longitudinal waves in a plasma

It can be read almost everywhere that plasma is the best convertor of transverse waves to longitudinal waves. I'm not much interested in the theory here. Rather, I would like to know how to do it in a ...
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Why can $Q$ be calculated by $f_0/f_{FWHM}$?

I found this expression for the reflection signal of a microwave cavity: $$ |\Gamma|^2(f) = 1-\frac{1-\Delta M}{\left(2Q\left(\frac{f}{f_0}-1\right)\right)^2+1}, $$ with $f$ the frequency, $f_0$ the ...
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Microwave waveguide position is not symmetric with respect to the center of the cavity

I am using a Panasonic microwave oven for some experiments. I found that the waveguide is not placed centrally on the side wall. The waveguide flap is closer to the back wall of the cavity than it is ...
yds1798's user avatar
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How to measure time varying electric field strength accurately in space and time?

I would like to know of any techniques that can be used to measure the electric field strength precisely and accurately in both time and space. I know that there will be physical/ practical ...
Christian's user avatar
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When temperature is only caused by translational kinetic energy, why does microwaves heat water by rotation? [duplicate]

I thought microwaves causing water molecules to rotate, thus raising the temperature of my food but temperature isn't caused by rotation or vibration degree of freedom: We also pointed out that ...
iwab's user avatar
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Why do some microwave meal instructions violate the 'Specific Absorption Rate' rule?

Do Microwave oven heating times grow linearly with Wattage? Calculating optimal heating time states that the product of the microwave power and cooking time should be constant. However, some meals ...
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Is it possible for microwave beam to pass through non-metalic materials?

Greetings fellow physicists. I have some questions about the ability of different electromagnetic waves to pass through materials that I hope you can clarify. It seems that microwaves can go through ...
Hooman Puyandeh's user avatar
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Why does my microwave turn on other battery powered electronics?

Situation: I have a 8-10 yr old LG microwave in a small alcove built into the cabinetry of our kitchen counter. I have a pretty cheap Bomata battery powered coffee scale that I store on the countertop ...
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Effective permittivity of multiphase system

I am simulating the microwave heating of a packed bed of solid spheres. This consists of a discrete phase made of the solid spheres and a continuous phase in between. In order to simplify the problem ...
cosmogato's user avatar
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Is the argument of zero tangential field components in wave guide walls a fallacy? Or: How EM waves "magically" find their correct transverse modes

I just came across a nice answer on Quora, explaining visually how wave guide modes can be constructed from the condition of zero tangential fields in the wave guide walls. In mathematical terms, this ...
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Is there laser operating at megahertz?

I have tried to find a laser with working frequency at megahertz by Google but failed. Is there exist one?
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Why does a microwave's faraday cage block microwaves but not larger wavelength radiowaves?

I read that the Faraday cage on a microwave door prevents the microwave radiation from escaping the microwave because the wavelength of the microwaves is "too large to fit" through the holes ...
Cole Pearson's user avatar
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How does 3cm microwave pass through a 0.5 cm grating?

This YouTube video prompted a question. If the wavelength of the PASCO microwave generator is about 3 cm, how do we explain that a significant portion passes through a 1/2 $cm^2$ screen? I have a ...
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What is radio frequency microwave energy used for? [closed]

Yesterday, the X-37B landed in Florida after 3,774 days in space orbiting earth since 2010. It was said to be transmitting radio frequency microwave energy towards earth for experimentation. What is ...
JustBeingHelpful's user avatar
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Why does my microwave oven affecting Bluetooth signals? [closed]

Today morning I observed something interesting while I was listening to music with Bluetooth earphones. I connected earphones to my mobile phone that was lying almost 20 feet away . Music was of ...
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Does 5G affect your physics experiment?

Our institution wants to lease a nearby roof for a 5G mast. Has anyone experienced the installation and operation of telecoms infrastructure - particularly 5G - significantly affecting physics ...
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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 ...
MikeTeX's user avatar
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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 ...
Werex Zenok's user avatar
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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,\...
Marco Toni's user avatar
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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 ...
user11937382's user avatar
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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 ...
AncientSwordRage's user avatar
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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 ...
Manu de Hanoi's user avatar
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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? ...
Sebastián Vansteenkiste's user avatar
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6 answers
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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 ...
Manu de Hanoi's user avatar
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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 ...
Aaronmacaron's user avatar
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1 answer
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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 ...
user6760's user avatar
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1 vote
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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 ...
user3141592's user avatar
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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 ...
plumpy's user avatar
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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 ...
adamwong246's user avatar
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4 answers
5k views

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 ...
Samyak's user avatar
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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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2 votes
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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? [closed]

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-...
ferocioussprouts's user avatar
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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 ...
Aumedi Wibisana's user avatar
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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 ...
Captain Trojan's user avatar
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5 answers
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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 ...
i like math's user avatar
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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. ...
Eric Hernandez's user avatar
4 votes
2 answers
377 views

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 ...
Razor's user avatar
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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 ...
Black Tea's user avatar

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