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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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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Leaked electric field in Transmission Line theory

In the previous image I can't understand why the leaked electric field in plate conductors is axial (On the same axis of propagation), And if it becomes axial then the wave in the conductor is not <...
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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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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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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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