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).

Filter by
Sorted by
Tagged with
1 vote
1 answer
55 views

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 ...
user avatar
  • 661
0 votes
1 answer
38 views

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 ...
user avatar
0 votes
1 answer
25 views

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 ...
user avatar
  • 1
0 votes
1 answer
37 views

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 ...
user avatar
1 vote
0 answers
48 views

Microwave Oven Radiation

I read that microwave ovens are allowed by FDA to emit max 5mW/cm2 electromagnetic radiation at about 5 cm from the surface: https://www.fda.gov/radiation-emitting-products/resources-you-radiation-...
user avatar
  • 111
0 votes
1 answer
17 views

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 ...
user avatar
  • 1,349
0 votes
1 answer
29 views

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? ...
user avatar
3 votes
5 answers
159 views

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 ...
user avatar
1 vote
2 answers
120 views

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 ...
user avatar
  • 11.4k
12 votes
6 answers
4k views

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 ...
user avatar
  • 297
-2 votes
1 answer
60 views

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 ...
user avatar
11 votes
1 answer
1k views

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....
user avatar
  • 883
0 votes
1 answer
32 views

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)=...
user avatar
  • 71
2 votes
0 answers
34 views

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 ...
user avatar
  • 11.4k
0 votes
0 answers
13 views

Field at exactly the cutoff frequency of a waveguide

What happens below or above a cutoff frequency is very well documented! I have never seen though a clear explanation (as a matter of fact no explanation) about what happens at exactly the cutoff ...
user avatar
1 vote
1 answer
14 views

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 ...
user avatar
0 votes
0 answers
49 views

How to experimentally orient the rotation axis in the Bloch sphere during Rabi oscillations?

Rabi oscillations are well known in the field of quantum physics. I have seen plots of experimental realizations of Rabi oscillations. However, I do not understand how to manipulate the rotation axis ...
user avatar
0 votes
2 answers
47 views

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 ...
user avatar
  • 1
-2 votes
2 answers
81 views

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 ...
user avatar
15 votes
4 answers
3k 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 ...
user avatar
  • 177
0 votes
0 answers
11 views

Scattering parameter oscillation

Why does scattering parameter $S_{11}$ for a two port measurement with a simple cable oscillate with frequency?
user avatar
  • 9
0 votes
0 answers
41 views

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 ...
user avatar
  • 11
2 votes
1 answer
26 views

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). ...
user avatar
  • 756
2 votes
1 answer
422 views

Is it okay to sleep with the wifi router next to me?

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-...
user avatar
1 vote
0 answers
23 views

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 ...
user avatar
0 votes
0 answers
11 views

Can we make a microstrip analog of a 3D microwave E plane Tee

I need to make the 2d analog of a microwave E plane tee.The microwave Eplane tee has 3 ports and it divides a wave input at port 3 into two 180 degree out of phase waves at the 2 output ports. I want ...
user avatar
0 votes
0 answers
27 views

Microwave from helmholtz coil

Can I create a microwave field in the center of a pair of helmholtz coils if I drive them at 3 GHz or will the electric component of the field cancel out?
user avatar
  • 23
1 vote
1 answer
164 views

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 ...
user avatar
0 votes
0 answers
17 views

Microwave relay antennas

Looking over the history of microwave relays I can see there are four distinct antenna design "periods". The very early systems used simple parabolic reflectors with dipole antennas, often ...
user avatar
35 votes
5 answers
3k views

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 ...
user avatar
  • 549
0 votes
1 answer
51 views

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. ...
user avatar
4 votes
2 answers
158 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 ...
user avatar
  • 53
0 votes
1 answer
112 views

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 ...
user avatar
1 vote
2 answers
66 views

Do slits cause light to become coherent?

In the young double slit experiment, you have a single slit followed by two slits. I believe it is the single slit which cause the light to diffract and become coherent and the double slit is to ...
user avatar
  • 41
0 votes
1 answer
43 views

Multiple frequencies microwave heating

I was wondering how to calculate the power dissipation density (electromagnetic losses) when two waves of different frequencies are used simultaneously to heat a dielectric object. Of course, this ...
user avatar
1 vote
1 answer
104 views

Why do electromagnetic waves hate discontinuities?

It's known (and it's the basis of many designs of microwave devices) that electromagnetic wave propagation in a medium occurs in a good way (i.e. without reflection and higher order modes excited), if ...
user avatar
  • 1,109
0 votes
0 answers
46 views

Microwave heater for heatin graphite crucible

I'm interested in melting alumina in a graphite crucible, some details here. As a tungsten heating wire apparently will oxidize rather quickly in a regular atmosphere, i was wondering if i can't heat ...
user avatar
34 votes
4 answers
9k views

Stood in front of microwave with the door open [closed]

I was cooking something in the microwave and opened the door early to check on it and the microwave didn't stop. I didn't realize this for a few seconds and when I did I shut the microwave off but I'm ...
user avatar
19 votes
7 answers
5k views

In a microwave oven, why do smaller portions heat up faster?

Sorry for brevity, but what is the exact physics explanation of why smaller quantities placed inside a microwave oven heat up faster than when you place a larger quantity of a similar material inside?
user avatar
  • 433
0 votes
1 answer
86 views

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 ...
user avatar
0 votes
0 answers
46 views

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 ...
user avatar
1 vote
0 answers
368 views

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 ...
user avatar
  • 123
18 votes
3 answers
2k views

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 ...
user avatar
0 votes
1 answer
151 views

How to explain mobile phone rings inside microwave oven? [duplicate]

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 ...
user avatar
  • 1,586
0 votes
0 answers
36 views

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 ...
user avatar
  • 186
4 votes
2 answers
253 views

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 ...
user avatar
20 votes
3 answers
3k views

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 ...
user avatar
  • 311
1 vote
0 answers
58 views

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 frequencies ...
user avatar
  • 160
0 votes
2 answers
119 views

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 ...
user avatar
1 vote
2 answers
183 views

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&...
user avatar
  • 111

1
2 3 4 5 6