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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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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 candid 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 ...
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1answer
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How could I build a polarizer for 12GHz electromagnetic waves?

I have built a gadget that can make pictures using ambient 12GHz radiation. The nature of the parts I used (commonly available satellite TV parts) means that I have selectable polarization on the ...
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1answer
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Why can a cellphone ring inside a microwave?

I placed my cellphone inside my microwave. This notwithstanding, my step mother was able to call me, again. Is it a normal thing or I need to change of microwave ? I believed faraday cage of a ...
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1answer
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The “watering hole” frequency versus microwave oven frequency

I recently learned about the "watering hole," a group of frequencies between 1.42 and 1.66 GHz. I also read that microwave ovens operate at 2.4 GHz. If 21 to 18 cm (1.42 to 1.66 GHz) is the resonant ...
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Question on Microwave Oven : [duplicate]

Energy of Electromagnetic Radiations is given by e=hc/λ. Implying shorter the wavelength more the energy. Cooking food requires energy. So why we cannot use Cosmic Rays with wavelength of about 0.01 ...
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Understanding the principle of photo diode signal generation

I have two lasers, both illuminate on a photo diode, i'm not very sure what's physically going on in the photo diode. My understanding is the following: The electric fields of both lasers add up and ...
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1answer
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How do microwave transformers avoid power loss through the skin effect?

I was reading about the skin effect and how the effect increases for higher frequencies. I also read that Litz wires can be used to counteract the effect, but usually only up 1 Mhz frequency. Is ...
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1answer
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How to devise a microwave power sensor?

I am fairly aware of the general thermistor/ diode/ thermocouple methods of sensing microwave power. Currently my requirements are simpler: A device that senses only microwave power incident on it - ...
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Standing wave ratio inside a waveguide

If there were microwaves being transmitted through the waveguide in the image below out the horn, and I place a sheet of metal in front of the horn (perpendicular to the propagation of the waves), ...
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1answer
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Microwave Ignorance

I have two identical ceramic coffee cups, but when I put them into the microwave (oven) with the same amount of water, for the same amount of time, the handle of one cup is discerningly hotter than ...
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1answer
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Mode expansion inside a waveguide

In the classic book by Collin (Foundations for Microwave Engineering, 2nd ed.), the author postulates on p. 278 that, given a waveguide structure that stretches along the $z$ axis with open ends (see ...
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Radar waves all waves not working under water

was just wondering why all waves don't work under water for? I know they work for 10 meters "but" after that they don't. Does it have anything to do with it's wavelength? Or is it just that the ...
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Transmitted energy and transmitted wave phase in microwave structures

I have two questions about waves in large microwave structures. So the system I'm currently working on can be simulated as lossless transmission lines put together to one long structure. Without ...
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Effect of mass of sample on the power required for microwave heating

Is there a relation between the power required for microwave processing and the mass of the sample processed? In a paper on rapid pyrolysis of wood, it was stated that, the power required per weight ...
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EM/Microwave interaction with neutral atoms and their particles

I'm not sure I understand this well, so please bear with me. I've read a few answers on here about electric fields from neutral atoms, but they aren't agreeing on it. In any case, these are the ...
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Do microwaves (photons) lose energy as they heat?

I understand that microwaves are able to heat water because their alternating electromagnetic fields flip water molecules (dipoles) up and down which increases the waters kinetic energy (thus ...
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Can a mesh shield keep food cold in a running microwave?

Please forgive my amateur physics knowledge. Say it's Thanksgiving leftover day. You load a plate with turkey, potatoes, cranberry sauce, and salad. Now it's time to heat your food, but oh no! You ...
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Does a MASER beam stay un-dispersed like that of a laser?

We know that a laser beam has a very low dispersion rate. Does the same apply for a MASER (Microwave Amplification by Stimulated Emission of Radiation) beam?
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Waveguide horn antenna & inverse square law

With a lab waveguide / horn antenna setup similar to image (without bends), we made the following measurements. Now we thought this could be used to demonstrate the observation of the inverse square ...
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Is long wave electromagnetic radiation hot? If so, why?

Both infrared radiation and microwaves warms up objects it meets, so therefore I wonder, is all long wave electromagnetic radiation hot? And if it is, why?
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Why does Skywave only work for a small frequency band?

So it is often said that waves in the HF band (3-30MHz) use skywave propagation to beam signals around the curvature of the Earth. My question is why is there this narrow limit to what is able to ...
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Transmission lines - Reflection co-efficient

I'm currently studying transmission lines off a internet resource here: http://alignment.hep.brandeis.edu/Lab/XLine/XLine.html Now at the part 'reflection co-efficient', the author writes "The ...
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1answer
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Is the polar nature of water a factor in its resonance with microwaves?

This schoolphysics webpage discusses some information regarding the heating of water using microwaves, and according to that page a common misconception that "Microwave ovens operate at a ...
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Why plastic covers on containers are compressed when microwaved?

These situations happen a lot around me since I always bring my lunch to the school. It is not just plastic warp, but my plastic container lid too. Unlike Why does plastic wrap grow, then shrink, then ...
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Magnetron Tube Emit Direction

for a project I am doing research on microwave ovens and their operation. I have researched most of the electronic components but I was wondering about one part, the magnetron tube. I have looked it ...
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Existing microwave trapped ion quantum computer?

In the recent paper Blueprint for a microwave trapped ion quantum computer, the authors envision a scalable design for a quantum computer, built from smaller ones implemented on silicon wafers, "using ...
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What happens in an empty microwave oven?

What it we don't put any food in a microwave oven? I.e. nothing to absorb the microwaves? Would the standing microwave modes in the 3D cavity be reinforced? Would there be too much energy in the ...
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What makes cheese so effective at absorbing microwaves?

Whenever I put a meal in the microwave which contains cheese, why does the cheese get hot before the rest of the meal is heated through?
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Hydrogen & Other Noble Gases in a Microwave

I was watching some Youtube videos of people microwaving helium and neon in a microwave. I could not find anything showing hydrogen in a microwave. However, as I was watching the videos I noticed ...