Propagating solutions to Maxwell’s equations in classical electromagnetism and real photons in quantum electrodynamics. A superset of thermal-radiation.

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31 views

How can there be E and B fields inside waveguides?

A hollow waveguide that is made of conducting material allows for the existence of an electromagnetic wave inside it which propagates from one end to the other. However, conductors are known to ...
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1answer
57 views

What causes electromagnetic waves to propagate in free space?

In free space, $\rho=0$ and $J=0$, so there are no electromagnetic sources/sinks. Maxwell's equations thus reduce to: $\nabla\cdot E = 0$ $\nabla\cdot B = 0$ $\nabla\times E = -\frac{\partial ...
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19 views

What does relative permitivity of medium mean and what does it depend on?

Does relative permitivity have someting to do with the polarization of medium , like for example how in inside the capacitor magnitude of electric field would be less due to a smaller opposing field ...
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13 views

the inner self-inductance of coaxial cable using integration

I'm trying to calculate the inner inductance of a coaxial cable using integration knowing that the answer is : $L=μl/8π$ i get the same answer when i take a cylindrical shell of thickness $dr$ but the ...
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1answer
35 views

Photoelectric effect on charged plate

As far as I know, to observe the photoelectric effect, one has to expose a metal surface to high-energy radiation. But what happens if the surface has a surplus of electrons? What is the energy needed ...
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60 views

Why is glass green?

When I look at a glass block at an angle the edges appear green, but when I look at the edge sideways, so that is directly in front of my eyes it appears transparent. Why?
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55 views

Speed of RF waves and IR waves is same as 3 * 10 ^8 m/s?

In space,if we want to measure the speed of RF waves and IR waves it will be roughly 3 * 10^8 m/s ( SPEED OF RF WAVES = SPEED OF IR WAVES = 3* 10^8 M/S ) is this correct ? The different in the ...
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1answer
39 views

Speed of light in vacuum in special relativity

In special relativity, the speed of visible light is defined as a constant. But visible light is only a small part of the electromagnetism field. So why?
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2answers
35 views

Difference between scattering and refraction?

I while back I learnt that when light is incident on a dipole the dipole will scatter the light, and when it is incident on a material of a different refractive index then the light refracts. From the ...
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2answers
38 views

Is the electromagnetic spectrum bounded somehow? [duplicate]

Is there a maximum frequency that an electromagnetic wave can support?
3
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1answer
45 views

Is the photoelectric effect 'Ionising Radiation'?

According to the definition on Wikipedia, ionising radiation is radiation which has sufficient energy to remove an electron from an atom. So a high energy gamma ray is definitely ionising, but visible ...
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2answers
51 views

Description of a photon and quanta

Could someone please help to clarify the difference between a photon and a quanta? Below is my current understanding - please correct me if I am wrong. A photon - is a 'wave particle' of 'light'. I ...
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1answer
898 views

Why is everything not transparent? [duplicate]

There is a related question on this site here: Why glass is transparent? Which explains that glass is transparent because the atoms in glass have very large energy differences between energy levels ...
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2answers
64 views

How can 2 EM waves null each other at a point but continue to propagate?

how can 2 EM waves (travelling in opposite directions) null each other at a point in space but continue to propagate beyond the point in space where they interact to null each other?
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23 views

Dependence of Noise Tolerance of waves

Electromagnetic waves are used for transmission of any message. And different kinds of waves have different noise-tolerance. If my guess is right then the noise tolerance is a property of wave which ...
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0answers
43 views

Why call it a particle and not a wave pulse?

My physics textbook says that photoelectric emission provides conclusive evidence for the particle theory of light. Apparently, since photoelectric emission only works at certain frequencies, we can ...
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1answer
71 views

Maximum wavelength of a photon/electromagnetic radiation?

This asked; What is the minimum wavelength of electromagnetic radiation? And also this; What is the maximum possible frequency and wavelength? The second question is contradictory; maximum ...
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4answers
135 views

Why do the edges of glass blocks create a shadow?

I have always observed that the shadow of glass blocks becomes darker as the glass is moved away from the surface where the shadow falls. And I know this is because refracted light rays from the glass ...
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2answers
243 views

What is the amplitude of the electric field in a laser?

I'm looking for reliable informations about the amplitude (not the intensity), in volt/meter, of the electric field in a typical laser. Or in other words : what are the typical amplitudes of the ...
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13 views

What dictates the range of EM radiation which can be produced by semi-conductor excitation (like LEDs)

Exciting semiconductors such as silicon carbide and gallium nitride can cause electroluminescence. I believe that by altering the chemistry of the semiconductor, you can alter the wavelength of the ...
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1answer
50 views

Does slowing light violate relativity?

Last year Scottish scientists managed to slow down photons in vacuum by changing their shape. Does this violate the special theory of relativity?
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1answer
28 views

Wave generated with particle excitement

To my understanding, an electromagnetic wave(infact two perpendicular fields) will be emitted when a particle(e-) shifts from higher energy orbital to lower energy orbital but what would be the ...
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1answer
63 views

Is it possible to strip the magnetic, or electric field from a photon?

A photon is made up of a magnetic part and an electric part, but we can see the existence of these fields without the other one so I would like to know if it is possible to somehow separate one field ...
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1answer
36 views

Characteristic room-temperature photon energy - is this nomogram wrong?

Reading this recent ars technica article on the James Webb telescope, something kept bothering me about the nomogram - shown below. The credit says it is from The Opensource Handbook of Nanoscience ...
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24 views

Is frictional heat just electromagnetic interactions creating infrared radiation?

Example: Rub your index finger on a sheet of paper and you will feel that it will get noticeably hotter Is the reason you feel this increase in heat (technically an increase in kinetic energy of the ...
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19 views

wave propagation modelling

what is the best modelling technique for modelling mm-wave propagation in electromagnetic environment. Right now,am working on how to use use Transmission-line matrix (TLM) and ray-tracing techniques
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1answer
40 views

From how far away could Earth's telescopes detect Earth like radio signals?

The Earth has been broadcasting human generated radio signals for about 100 years now. If a nearby civilization were broadcasting similar radio signals, could we detect them with our own radio ...
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1answer
35 views

Is every electric wave is an 'electromagnetic wave'?

Is every electric wave is an 'electromagnetic wave'? Why we only assume the electric field only?
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1answer
49 views

In a waveguide, where does the energy in attenuated waves go?

In an electromagnetic waveguide, there is generally a "cutoff frequency." Electromagnetic waves with a frequency that is lower than this cutoff frequency will not propagate at all -- i.e., they will ...
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1answer
20 views

When thermal IR gets reflected from an object, does it change its wavelength (frequency)

I'm working with thermal infrared (IR) cameras to detect human thermal radiation. I notice I can easily distinguish non-human objects throughout the camera's field of view, though all are at same room ...
3
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1answer
41 views

Momentum transfer of Light to Object

Can light made of photons in theory topple lets say a car? I know basic photon energy is hv where v is frequency. So according to conservation of linear momentum, if high enough and large amount of ...
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1answer
76 views

Characteristics of electromagnetic radiation

Is it possible to change the wavelength of an electromagnetic wave without a change of medium?
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1answer
54 views

Why are magnetron apertures in home microwaves so small?

I'm curious why magnetrons from a home microwave like in the image below can have an aperture between the magnetron cavity and the waveguide that is significantly smaller (2-6mm usually) than the ...
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0answers
46 views

What can I put in my microwave oven that won't get warm?

I have a fuzzy understanding that microwaves heat food because the waves interact with polar molecules in the food, causing them to vibrate, and the vibrations are heat? Correct me if I'm wrong. To ...
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1answer
33 views

How close do waves have to be for their wave functions to cancel? [closed]

I was thinking about waves canceling today and started wondering about this. Is there an equation relating the lateral separation of two identical but out of phase waves to how much they are canceled? ...
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3answers
217 views

aLIGO potential signals mimicking GWs not considered in the team publications? [closed]

[EDITED to accommodate info from the comments] Among the local atmospheric electromagnetic potential sources of a signal capable of mimicking the waveform of a GW not sufficiently considered by LIGO ...
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30 views

What is the direction and orientation of the modulation frequency in AM when it uncouples in flesh? [closed]

Cancer research shows that dividing cancer cells could be killed with frequencies from 100 kHz to 300 kHz (Kirson Tumor Treating Fields or TFF). The early research used a monofrequency that was ...
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57 views

Do photons traverse through the vacuum of outer space as a helix? [duplicate]

I’m trying to understand “Electromagnetic waves”. If electromagnetic waves traverse as a helix then do photons traverse as a helix?
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5answers
89 views

How is the electromagnetic field made?

I know that an electric field is created by a particle with a charge and that a magnetic field is created by a moving charge but how do they combine to make a electromagnetic field?
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51 views

What happens at the point of welding iron?

What is the physics behind welding iron? It is obviously the electricity that causes the two metal parts to fuse but what is the role of the welding rod and why is it said to damage your eyes when you ...
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2answers
77 views

Why do electromagnetic waves diffract? [duplicate]

The expansion of electromagnetic waves due to diffraction can be easily explained with Huygens' principle (and in introductory courses this is usually how it is explained). But Huygens' principle is ...
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2answers
75 views

How does electromagnetic radiations penetrate?

I am reading about the discovery of subatomic structure which includes all these things radioactivity, alpha rays, gamma rays, x rays et cetera. I read that electromagnetic radiations are energy ...
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2answers
78 views
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1answer
86 views

Why are electric and magnetic fields perpendicular in an electromagnetic wave?

I want to know why electric and magnetic fields are perpendicular in an electromagnetic wave and what would happen if they weren't.
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1answer
36 views

Radiation frequency from an accelerated charged particle

My understanding is that a charged particle, when accelerated emits EM radiation. In a situation where a charged particle is briefly accelerated in a straight line it should produce a propagating ...
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1answer
107 views

What is the nature of the magnetic fields? [closed]

In this question, I am hoping to find out if there is an explanation to the magnetic hidden forces. In other words, what causes these fields? Is there any suggested theory, or any confirmed ones ? ...
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1answer
48 views

How to visualize electromagnetic waves?

Can someone please explain to me how to visualize an electromagnetic wave in 3D space? I have struggled for a long time now trying to understand how a WiFi signal could reach a device if it looks like ...
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2answers
32 views

How is it possible to even develop any current in an inductor?

Potential difference across an inductor (ie p.d. between current exit point and current entry point) is given as $$V= -L\frac{di}{dt} -iR,$$ where $L$ is the inductance of inductor and $R$ is its ...
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1answer
56 views

Vacuum chamber that prohibits EM wave propagation

Is it possible to create a vacuum chamber (something like vacuum tube) in which EM wave propagation is prohibited and EM radiation does not exist at all?
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1answer
68 views

How do integral representations of $\mathbf A$ and $\Phi$ satisfy Lorenz condition?

The following are the integral solutions of the potentials, obtained from the retarded potentials (by a Fourier transform): $$\mathbf A (\mathbf r) = \frac{\mu_0}{4\pi}\int_V \frac{\mathbf J (\mathbf ...