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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My coffee cup is only heated at the top [closed]

My coffee cup (any liquid) is only heated at the top of the cup. The bottom is normal temperature regardless of the cup when heated in microwave. How so?
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Does graphite absorb radiation? [closed]

Can natural graphite absorb electromagnetic radiation (or any radiation for that matter)? I've searched about this on the internet but found few sources that mention it; however, there are some sites ...
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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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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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Heating a mug of milk in the microwave [closed]

Yes, this is a homework question. We are told: Ann wants to make 0.5 litres of cocoa for breakfast and takes milk from the fridge which is at 4 celsius. She pours it into a porcelain mug of mass 0.4 ...
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How can electromagnetic waves reach a cell phone in Faraday cage?

is there any way to make electromagnetic waves reach a cell phone in Faraday cage although conductor surround cell phone everywhere? can we pass current through conductor to make charges move as a ...
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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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How to explain mobile phone rings inside microwave oven?

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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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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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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How do microwave kilns work?

I have recently been doing some research into the working principle of a microwave kiln, and have run into a few things that continue to confound me. The first of which being that the devices ...
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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 ...
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How does this microwave kiln achieve such good insulation?

I am reading on Amazon about this microwave kiln, I am wondering how it achieves such high temperatures inside a microwave. What unusual material is this? Safety: microwave kiln material for high ...
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Why does food microwave more evenly if you organize it in the shape of a torus?

Any lover of leftovers knows that if you push your food to the edge of a plate and form a donut shape before microwaving it, the food heats up much more evenly and you don't get the "cold middle&...
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How could a microwave's magnetron break down due to the presence of metal inside the oven?

I have a combined microwave oven/grill (Ikea Granslos) that broke down recently. It looks like this: There is a wire shelf in the middle that I've always assumed to be compatible with both baking and ...
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Electromagnetic wave patterns in waveguides for different modes like TE10, TM11

I have read about different waveguide and their different modes like TE10, TE11, etc. In many books, the EM wave patterns are given, where they were said to be drawn from the waveguide's equations. ...
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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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Hydrogen & 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 ...
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Advantages/disadvantages of a cylindrical microwave oven cavity in comparison to a rectangular cavity

Why are rectangular cavities preferred for standard microwave ovens with a frequency of 2.45 Ghz? What is the reason that you can hardly find a circular cavity? What are the disadvantages of ...
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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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Considering the history of microwave Background radiation, was it ever in visible range? When will it fall to be able to heat water like in our oven?

Please do provide assurance of what formula you used and that you did the calculations for the answer. Thanks. My back of letter calculation says that CMBR was never in visible range since it became ...
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What is the purpose of resonators in quantum circuits?

I have been studying about quantum circuits, and I have come across resonators or microwave resonators multiple times. I do have a vague idea about them but I am not able to understand what is their ...
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Superposition of Microwaves experiment? How does it work?

Please can someone help me out with this experiment and see if this is correct? So the experiment consists of one metal sheet that fully reflects microwaves (and is fixed in its position), and the ...
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Surface Roughness of a material in CST

I am adding an aluminium with a rough surface in CST Studio, but there is only thickness input (how thick the rough surface is), but as per ISO standards they are different types of rough surface with ...
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Ferrite material in CST Studio

I want to add a ferrite material in CST Studio for shielding effectiveness simulations, but not able to find any dispersion data for the material. I want to add a ferrite material in CST Studio for ...
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Electric fields with different frequencies, total intensity?

What happens when electric fields with different frequencies are combined? Is it possible to calculate the intensity of the total electric field? For a project, I need to simulate a brain treated ...
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How I simulate this in CST Studio? [closed]

I am trying to simulate this coaxial transmission line setup for EMI shielding. Placed the Aluminium sample as seen below (in the middle). I am new on this software, learned simulating the coaxial ...
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Cooling at a Distance

We have microwaves. Microwave ovens convert electricity into microwaves, specifically waves that resonate with water to make it hotter, thus heating my pizza in 3 minutes without disintegrating the ...
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Does the energy comsumption of a microwave depend on the amount of food inside?

I measured the heat absorbed by water in a microwave, and it was about 80% of the max. power of its specifications. But when the amount of water decreases too much (100 g or less) the efficiency ...
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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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Attenuation in microwave and optical communications

I have read that the attenuations of microwave transmission lines and optical fibers are ~1 db/m and ~ 0.2 db/km, respectively. I understand that these values depend on the geometry, design, and ...
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How do microwaves heat moisture-free items?

Today I learnt that microwaves heat food by blasting electromagnetic waves through the water molecules found in the food. Does that mean food with 0% moisture (if such a thing exists - dried spices?) ...
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Does the cavity magnetron in a microwave oven produce x-rays?

It seems like it should due to bremsstrahlung, since we're talking about electrons with 5-7KeV of energy slamming into the walls of the device, but I've found no information about this online, so I'm ...
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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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How many photons are in a microwave oven?

I have always had trouble connecting the picture of classical electromagnetism with the idea of photons. To make this connection better I'd like to ask the following question. How many photons, at an ...
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Is higher frequency electromagnetic radiation more harmful than lower frequency radiation?

Wireless devices operating on electromagnetic waves have become indispensable part of our daily lives. At the same time, it also raises concerns about ill effects of such radiations on human body. ...
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Why does a cold glass container when heated in a microwave breaks down? But a container at a room temperature does not?

I have noticed that when I take some eatable kept in a glass container, out of the fridge, when they are already at a low temperature (around 3-4 degrees) and then try to heat it up in a microwave ...
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How to read a meter for radio and microwaves?

I am not clear on how to read this meter for radio waves and microwaves. The bottom band shows it measures from .01 to 1. First, I'm not sure what the units mean (mW/cm2). Radio waves are from 30KHz-...
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What piece of technology is able to record the exact phase of microwaves?

I read that in VLBI, the signals of microwaves are recorded and then later combined. A famous example of this is the Event Horizon Telescope which imaged the black hole. Presumably, the telescopes ...
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Do microwaves break hydrogen bonds?

We're told that the photon energy of microwave frequency radiation ($\sim 10^{-5}~\text{eV}$) is not high enough to break hydrogen bonds. But if that's true, how does dielectric heating of water work?...
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As with infrared pictures, would it be possible to see 2.4GHz waves as light?

I have seen many pictures of stars that were taken in the UV or IR spectrum. Others have pointed out that they are scaled down so as to map to visible elements within our capabilities. Could Wi-Fi ...
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Why does a tube of frozen yogurt heat at only one end in a microwave oven?

The tubes of yogurt have a shell of thin plastic, with a single lengthwise seam and sealed at each end symmetrically apart from a small cut to initiate tearing at one end. They are of internal length ...
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Potato Cooking Room [closed]

In the TV show "Murdoch Mysteries" (S12E01) Detective William Murdoch has a an ultra-modern (for the Edwardian period) house built. It includes a "potato cooking room" which is essentially a broom ...
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Research that explains why it‘s fine to microwave a spoon but not a fork

I‘ve found plenty of articles explaining this and understand that it has to do with voltage differences at sharp corners of the object, but could find no direct research sources. Does someone know a ...
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Faraday cage for 5G?

I'm interested in making a faraday cage that will block both standard and 5G wireless signals- essentially to make a tabletop box that people can put their phone in to be completely undisturbed, and ...
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Why non-ionizing radiation is non-ionizing?

From Wikipedia I read that non-ionizing radiation "does not carry enough energy per quantum (photon energy) to ionize atoms or molecules". https://en.wikipedia.org/wiki/Non-ionizing_radiation#...
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Is it possible to converting electromagnetic waves to each other?

For example I have a source that emits X-Rays, is it possible to turning them into visible light or micro waves with the same energy as it was xray (I mean, can I change the frequency or the ...

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