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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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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Heating a mug of milk in the microwave

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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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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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?

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 ...
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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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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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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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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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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 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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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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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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Klystron output voltage, cavity physics

Can you please explain why almost nowhere do I see such a parameter as the output voltage from a klystron, it's easy to find the DC accelerating voltage of the beam and the electron bunch densities ...
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How come a mobile phone signal is blocked by aluminium foil, but Wi-Fi gets through?

Major puzzle for me. I have done a demonstration in lectures for years now, where I show that a mobile phone call can be blocked by wrapping the phone in a single sheet of standard Aluminium kitchen ...
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Why does a wave of single frequency travelling through the waveguide has group velocity?

Suppose we have a waveguide which is fed with electromagnetic wave having a single frequency of say 4GHz, if we are given the cutoff frequency we can determine the group velocity, but in order to ...
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Is there any factors depends for electromagnetic waves?

I am staying in hostel. One person said me that he is getting better connection with the wifi when the door is opened. I am wondering that what an electromagnetic wave can do with the door? Is there ...
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Might a cast iron pan set on top of a microwave oven affect the operation? [closed]

Our microwave seems to take longer to get the job done these days. I notice that someone is storing a large, heavy cast iron pan on the top of the microwave. Is there any way at all that it is ...
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Why are there different explanations of microwave oven heating, eg dipole alignment vs absorption? Is it quantum vs non-quantum?

There seems to be different explanations of how microwave ovens work. Here are the two basic forms of explanation I've heard: A. As microwaves pass through, the molecule dipoles try to align with the ...
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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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Charge Distribution on a Strip

let's consider a microstrip line connected to a voltage source V0 (applied between the strip and GND plane). According to foundation for microwave engineering (collin) book, the surface charge density ...
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Why and how does a microwave cavity confine resonant frequency inside it, not other frequency waves?

In microwave oven, the dimension of the chamber is determined according to 2.45 GHz frequency (or 12.2 cm wavelength). The chamber is made of metal and it should reflect all microwaves. Why does this ...
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Why standing wave is needed in microwave oven?

In microwave oven, standing wave is created in chamber by reflecting from metal surface. Do we create it intentionally? Is there any special advantages of it?
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About blocking of microwaves

When a phone is inside microwave oven and if we call it using wifi the phone doesnt recive call as frequency of wifi is same as frequency of wave generated in oven as there is a mesh like thing which ...
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Why do metal object in the microwave heat up while the walls stay cool?

I just came accross Why is Microwaved mac & cheese burnt where they touch? and discussed it with a colleague. We understand that metal objects heat up due to the eddy currents induced by the ...
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Why is Microwaved mac & cheese burnt where they touch?

After reheating cold about 1.5 oz. of Annie's Mac & Cheese shells for 15 seconds on high power in the microwave, the mac & cheese was burnt black only at certain points where the pasta is ...
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Is a Microwave oven without a faraday cage a health hazard?

Microwave ovens have something of a Faraday-cage/shield to keep from leaking (emitting) EM radiation. What would happen if the shield or the door was removed? No doubt it would be less efficient as ...

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