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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21 views

What's the difference between source current and conduction current?

Related Going through Pozar's Microwave Engineering, we have a derivation of Poynting's theorem which begins as follows. "If we have an electric source current $\bar{J_S}$ and a conduction current $\...
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What factors affect the amount of microwave absorption?

I am planning to do an investigation on factors affecting the amount of microwave absorption. I understand how microwave radiation heats objects, but do factors such as color affect the amount of ...
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Is there a difference between metal waveguides in microwave frequencies and dielectric waveguides in optical frequencies?

Do they work the same way? Do metal waveguides in MW also work through total internal reflection like in optical waveguides?
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Sci-Fi weapon: Satellite shooting laser beams down to earth? [closed]

The range of one of these is stated to be 700m. Since it sends out electromagnetic waves the only problem I see with limited range is the beam divergence. Atmospheric absorption is minimal so slapping ...
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Reflection Coefficient — propagation over a plane earth

In Section 2.1.2 "Propagation Over a Plane Earth" of [1], the author wrote: The reflection coefficient, $R$, of the ground depends on the angle of incidence, $\theta$, the polarization of the wave, ...
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Is there any danger standing in front of a household microwave? [duplicate]

I have noticed that on the door to microwave ovens there is a metal gridded screen. Is the purpose of this screen to construct a Farraday cage so none of the radiation can escape? If so, does this ...
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Does the microwave generating component in a microwave operate under the same physics as an antenna radio transmitter?

Essentially does the component of a microwave which generates those microwave photons operate using an AC power supply connected to a broken circuit which causes an oscillating dipole to radiate ...
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Can air be ionized using microwaves?

I've read about the concept of a laser induced plasma channel where air can be ionized to form a plasma using laser light. Can this be done or is it hypothetically possible to ionize air with ...
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5G networks and health concerns

Are there any peer reviewed journals on 5G networks and health concerns? I know very well that 5G radiation is of low frequency and non-ionizing and some concerns are related to the power of the ...
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How do ionizing and non-ionizing radiation interact with each other?

Given an ionizing radiation $ X $ and given non-ionizing radiation $ Y $, how does this radiation 2 interact with each other? For example I have X-rays (ionizing radiations) and Microwaves (non-...
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Why does an aluminum foil spark inside a microwave oven? [duplicate]

I did an experiment today. I put an aluminum foil inside the microwave oven thinking that nothing would happen. But contrary to my expectations it started sparking badly. I looked for answers on the ...
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X-rays / Gamma rays “oven” vs microwave oven

Let's imagine a seller scammed you and sold you a Gamma rays / X-rays "oven" instead of a common microwave oven. The power consumption would be the same as a common microwave oven, i.e. about 1 kW, ...
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Microwaves and Water Molecules: Radar vs Cooking

I am studying microwave radiometry and confused over this apparent contradiction: Microwaves emitted at 2.45 GHz (~15 cm) are absorbed by water molecules, causing the molecules to rotate under the ...
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Are kitchen microwaves in the audible range?

The waves of a typical kitchen microwave oven have a wavelength of 12cm while the audible spectrum is between 1.7cm and 17m, so one might think that they overlap and that kitchen microwaves should be ...
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Are 5G signals dangerous? [duplicate]

Ive been seeing a lot lately on the dangers of 5g and exposure to the internet and mobile signals but I dont understand why they are considered harmful when the 5g frequency band will be around 25 Ghz....
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How cavity magnetron works?

I've found an explanation on explainthatstuff.com. There are these electrons from the cathode that are going around in a circle (because of the magnetic field), passing next to the cavities. Then it ...
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Why do we have to switch off mobile phones during flight in airplanes? [closed]

During take offs the flight attendant makes sure that mobile phones are switched off (or maybe turned in airplane mode), why is that necessary? (I suspect that there is something to do with physics ...
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Concept of polarization in microwave rotational spectroscopy

I am trying to understand the concept of polarization of molecules after they are excited by a microwave pulse. The context is: The complexes are produced in a pulsed supersonic jet expansion of a ...
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How do microwaves communicate with satellites?

If microwaves only penetrate up to a few cm of food in a household appliance before being absorbed and transferring energy to water molecules, than how are microwaves able to communicate through long ...
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The effect of dielectric bridges on the impedance of a coplanar waveguide

I'll start with some context, but feel free to skip to the third paragraph for the concrete question. I also posted it on the electronics stackexchange, but I think it might have some more chance here ...
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81 views

Are microwaves sinusoidal or is that just a model?

I know that projectiles are parabolas because I can derive that from constant acceleration. And the height of a Ferris wheel rider vs. time is demonstrably a sine wave. What is the underlying thing ...
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Why microwave oven makes dried bread soft?

This is an old age trick: if you have some bread that became dried and you put it in the microwave few tens of seconds (10 to 30 for top results) you get a nice soft and warm loaf as if it just came ...
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Where in microwave ovens things warm faster?

I want my mug to boil as soon as possible and I prefer not to throw energy away. Where in microwave ovens things warm faster?
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Can radio waves be harmful to us?

I was studying about Microwaves and their action on water molecules in heating up the food. This all is probably due to Microwaves have wavelength such that it can be absorbed by water molecules (am i ...
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Microwaves in other media

I saw a video on how microwaving grapes make plasma. He said that the refractive index of microwave is about 10 inside the grape. Now, we don't know the wavelength of the microwaves in the grape or ...
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Do conductors reflect Wifi signals? If so why?

I know electric field can't pass through conductors, but I have seen people surround their wifi router by soda can (not entirely) for better signal strength. I want to know what really happens there.
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Microwave Grilles

Bit of an applied physics question here, to do with microwave ovens and the grille in the door through which you can see. My understanding has been that the grille works because the waveform of the ...
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What is the difference between the microwave photon and microwave radiation?

I'm new in quantum optics and I need to know that when a detector operates in microwave frequency range, which of microwave photon or microwave radiation takes part in detection? I suppose that the ...
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How can I beforehand determine whether a material is a good candidate for a microwave sensor?

Is there a table of some sort or formula where I can determine before I test the material under a microwave sensor whether it will allow the microwaves to pass through and if so at what depth. for ...
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If visible light has more energy than microwaves, why isn't visible light dangerous?

Light waves are a type of electromagnetic wave and they fall between 400-700 nm long. Microwaves are less energetic but seem to be more dangerous than visible light. Is visible light dangerous at all ...
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Why doesn't the escape of electromagnetic waves from a microwave depend on the reference frame, because of the Doppler effect?

If an observer traveling towards a microwave oven at almost the speed of light blue shifts the microwaves enough to be visible light, how can the mesh on the oven door still stop to waves from ...
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Common microwave absorbing substances

I'm looking to demonstrate to class of students how microwave absorption works, but I need something relatively common which I can easily make into a board. Does anyone have any suggestions for ...
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Could a microwave oven be tuned to defrost well? [closed]

Typical microwave ovens do a lousy job of defrosting because liquid water absorbs their radiation far better than ice. So once a spot melts, it will quickly rise to cooking temperature while the rest ...
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When you cook food in a microwave oven, why does't the plate get cooked? [closed]

When you cook food in a microwave oven, why doesn't the plate get cooked?
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How is the Solid in Oven centre Hottest [closed]

When a solid (any material) is placed in an oven and heated, the theory of radiation works I guess. How it the centre of the solid the hottest and not the surface of the Solid which actually receives ...
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Microwave cooking

This is just a little curiosity I've had, and I wonder what y'all think: I am poaching a chicken egg in a small (about 4 in. diameter) glass dish in my microwave. Let's assume the microwave is set on ...
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Does attenuation to RF waves increases with frequency?

I heard somewhere that RF waves at high frequency such as above 2GHz face more attenuation while passing through air, buildings and due to humidity as compared to 800Mhz and 2) Waves at 30-40GHz ...
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Which wave is widely used in waveguides?

I've studied that the rectangular waveguides are widely used because they have less cut-off frequency and as we know that the cut-off frequency is one of the major factors for waveguides. The article ...
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Why don't we use infrared light to heat food?

Why don't we use infrared (IR) or even the far IR just to heat food in a microwave oven instead of, of course, the conventional 2.45 GHz microwaves? Don't people call IR heat waves?
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Why we don't utilize most of the radio or microwave spectrum?

WiFi is from 2400-2500MHz or from 5000-5100. Fm Radio is 87-108Mhz, Phones : 450-3400Mhz But most of the spectrum is "wasted". For eg - Why we don't use above 5Ghz?
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What is the maximum speed of waves in stagnant water?

I want to learn the maximum speed conditions for a wave in a fluid. I think, Which mechanism causes this limited speed? And How? The water is an understandable example for me. By this question, I ...
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Subwavelength aperture vs microwave oven mesh

I am trying to understand why some subwavelength apertures radiate such as https://lo.epfl.ch/wp-content/uploads/2018/08/OE_14_10410_Oct2006.pdf and why others don't. For eg. the mesh inside a ...
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Are microwave-generating devices (gyrotrons) in the ITER system phased to heat plasma?

Provided electricity from grid is converted and supplies 24 gyrotrons, which generate electromagnetic waves, which in turn, will transfer their energy to the electrons of the ITER plasma to heat it up....
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Why does the presence of multiple items in a microwave require you to cook them longer than you would with the singular item? [duplicate]

I am familiar with the physical explanation as to why microwaves heat up food: the rapidly fluctuating electric field exerts a torque on the dipole of the water molecules resulting in vibration and ...
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RF signal on wirebonds

I am curious to know how RF signal is transmitted through wirebonds. I thought that in microwave transmission lines, the energy was stored in electric and magnetic fields inside the dielectric ...
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Internet - mobile phone vs wifi

wifi cost me like 30USD while mobile internet 10USD, I thought to save this monthly bill by purchasing a mobile-phone-router. The only thing that blocks me from that is radiation. I'm far fetched ...
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How is millimetre wave generated and why it cannot go higher to terahertz frequency?

I have been trying to find out how millimetre wave (3 GHz to 300 GHz) signals are generated but didn't find much. And I knew for some reason this method cannot generate THz electromagnetic waves, that ...
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Are there photographs taken in only the microwave spectrum?

I've seen many cameras and photographs of light in infrared, visible, and ultraviolet. And many photos of space in all areas of the EMS. Are there any photos of landscapes or architecture in microwave ...
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Blocking WiFi with Faraday cage [closed]

As part of a project I'm trying to prevent WiFi transmission of frequency 2.4 GHz from reaching a Raspberry Pi via a Faraday cage. Would a 20 micron aluminum foil do the job?
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Does a heat stone heated in microwave oven emits microwave? [closed]

I have a heat stone which functions just as heating pads. One concern is that it is heated in microwave. Sometimes I give it to my kids. One day a thought came to my mind that what kind of wave does ...