# All Questions

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### Shape of wavefronts for transverse modes in electromagnetic waveguide

I've been able to confuse myself about the shape (i.e. surface ripple/bend/tilt) of wavefronts for transverse modes in an electromagnetic waveguide, like a rectangular cross section waveguide with ...
142 views

### Do accelerated moving electrons radiate electromagnetic energy?

Do accelerated moving electrons radiate electromagnetic energy? Generally speaking, the charge should absorb energy instead of radiating energy in the acceleration stage, and release energy in the ...
38 views

### Would fast oscillating charged object emit light?

If I were able to mechanically oscillate an electrically charged object at frequencies of 430-580 THz, would the object emit light?
13 views

### How to incorporate refractive index in transfer matrix method

I need to determine the TE and TM reflections at the interface between a uniaxial crystal and air, using a matrix-based method, such as the TMM. I can do so using the Fresnel equation with ease, but ...
23 views

### Poynting vector flux on a closed surface

What does the flux of the Poynting vector through a closed surface represent? I know that the flux of the Poynting vector on a certain surface represents the power flowing through it. But if the ...
17 views

### Poynting vector flux in a tube (geometrical optics)

Let's consider the following tube (defined as the solid described by two arbitrary surfaces dA1 and dA2, and by all the rays which connect their boundaries): I read in a textbook that, because of ...
20 views

### Electric field from the intersection of two spheres with different charges

This question is repeated a lot, but I for two spheres with different charge densities, sphere one with radius a centered at the origin and charge density $\rho_1$, and sphere two with radius centered ...
58 views

### How can changing magnetic field produce instantaneously the electric field and vice versa? [duplicate]

Maxwell's curl equation for electric field says that time varying magnetic field produces electric field instantaneously but nothing can happen instantaneously according to special relativity. What is ...
15 views

### Guided propagation in transmission lines

Can you help me on understanding why we may say this transmission line the propagation is guided and there is not any radiation? It is a 2-conductors transmission line, in which the conductors are ...
43 views

### Can I think Transverse Modes in optical waveguides as an contructive interference phenomenon?

I am studying about Transverse Modes formations in optical waveguides. Q1. I got an impressions that this is a constuctive interference phenomenon. while waves that have phase difference 2pi*m; for ...
63 views

### Skin Effect Explanation

I do not understand some things about the Skin Effect. Its Wikipedia definition is: Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor ...
33 views

### Help me distinguish between an Amperian loop and a surface

This image is from the Resnick-Halliday-Krane textbook. These images have been used to see that a correction was needed in Ampere's circuital law. What I am confused about is, how are the two end ...
36 views

### Biot - Savart Law and time - variable current [duplicate]

Is the Biot Savart law valid also with currents which are functions of time (for instance a sine wave)?
31 views

### Helmholtz equation and sources

it is known that starting from the Maxwell equations it is possible to get the following Helmholtz equations: In time domain it corresponds to a sinusoidal EM field, according to the wave equation: ...
13 views

### Most general case for Optical Fibers eigenvalue equation

In the system of equations leading to the eigenvalue equation for Optical Fibers, books always avoid the $\phi$ dependence, as mentioned in this previous question. This, however, implies some ...
107 views

### Does a vibrating neutral object emit EM radiation caused by the vibration?

Does a vibrating neutral object emit EM radiation caused by the vibration? If the object is a molecule, does it radiate? and if the object is a atom? I am not refering to thermal radiation. It does ...
12 views

### A parallel between eddy current and Beer-Lambert law

For AC current flowing in wire eddy currents are the reason for current density decay as we move towards the center. Similarly, in Beer-Lambert law, for electromagnetic plane wave impinging on ...
93 views

### How do I transform flux density into temperature?

I have flux density data from Planck mission (in Jy) - measure in a certain frequency - and I would like to transform it to temperature data (Kelvin). I'm not sure if I should use Stefan Boltzmann's ...
84 views

### Why is the stress-energy tensor for electromagnetic radiation traceless?

A photon gas obeys the equation of state $\rho=P/3$ and hence $T^{\mu}_{\quad\mu}=3P-\rho=0$. (Can also be seen by expressing the stress energy tensor in terms of of the electromagnetic tensor as ...
73 views

### How is light as electromagnetic waves produced?

One of the upvoted answers to Why don't electromagnetic waves require a medium? says that the electromagnetic field is the medium for electromagnetic waves. It went on to say that if the ...
13 views

### Plasmon modes of cylinder metalic particle

Solving Laplace equation gives plasmon modes of spherical metalic particle radius $R$, plasma frequency $\omega_p$. Famous result is $l = 0, 1, 2, ...$ $$\omega_l = \sqrt{\frac{l}{2l+1}} \omega_p$$ ...
38 views

### EM-wave interaction with particles

I'm interested in EM waves acting on particles, but have a poor understanding since I haven't yet read a proper EM book and currently am doing more mathematical stuff. I've looked through a couple of ...
132 views

### What is the frequency distribution of the electromagnetic wave emitted by a charge accelerating along a given trajectory?

Charged particles radiate when accelerated.From a few other answers from Physics Stack exchange like What is the frequency of a photon emitted by an accelerated charged particle? and How ...
35 views

### Changing Refractive Index

Is it possible that the refractive index of a material could change?if so,what are those factors and what kind of variation could they bring?
131 views

### Does light carry heat both are same thing or different? [duplicate]

In many books it is written that light is an electromagnetic wave, as we know there does not exist any oscillator that can oscillate an electron with a frequency of light. My question is, how can we ...
51 views

### Why is light moving transversal?

This question will be in some way complicated for different reasons - I am no physicist, I know about things like wave-particle duality, that the tranversal wave motion comes from change in electric ...
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### What is the force corresponding to Lamor's formula for EM radiated power?

The rate at which electromagnetic energy is radiated is given by Lamor's formula. What is the corresponding rate at which momentum is radiated and hence force to this?
83 views

### How did Maxwell figure out the speed of light?

The Wiki article is about 2 graduate years of physics beyond my understanding. What is a good high-school rendition of his thought process: regarding his use of the "distributed capacitance and ...
66 views

### Propagation of mechanical waves in vacuum

It is known that, while electromagnetic waves can propagate in vacuum as they do not need a medium, mechanical waves (e.g. sound waves) cannot. However, vacuum has vacuum fluctuations, where (virtual)...
110 views

### What does Maxwell's equations predict for the propagation of EM waves converging to a point?

Maxwell's equations model EM radiation as propagating away from an accelerating charge. Suppose instead the propagation of this EM radiation is reversed and presented as a source-free boundary ...
66 views

### Polarisation of EM waves

My textbook reads 'The plane of polarisation of an electromagnetic wave is defined as the plane in which the electric field oscillates.' What exactly does this mean? I understand that an EM wave ...
27 views

### Optical fibers field analysis, $\phi$ dependence not considered

In optical fibers, the core (with $\varepsilon = \varepsilon_1$) is usually represented by a cylinder of radius $a$, whose axis coincides with the $z$-axis in cylindrical coordinates. The cladding is ...
60 views

### Is the speed of Magnetic field infinite?

My real question is: From Amperes law we know that there is no magnetic field outside of the coaxial cable because the magnetic field generated by the inner wire and outer shell are equal but in ...
10 views

### Resources for spin-stabilized magnets

I will be carrying out an experiment investigating the factors that effect the speed of a spin stabilized magnet. Can someone provide resources or articles that talk about/ have formulas related to ...
40 views

### Why does the electric field and not the magnetic field remains in the same direction after reflection from a medium?

I was reading up about reflection and transmission when an electromagnetic wave is normally incident on a surface. I came across this figure : My question is why is the direction of electric field ...
24 views

### EM- waves in anisotropic medium

When ElectroMagnetic waves from vacuum enter the anisotropic medium. If the $\epsilon$(permittivity) matrix is diagonal (with not all diagonal entries being equal). There'll be two waves in the ...
45 views

### Is the Electric and Magnetic field in an EM wave interacting in the same way static E and B fields?

Sorry by the title, I don't know how to ask this: What happens to a charge when some EM wave passes across it? If we have an EM wave with really low frequency, is this basically the same as having a ...
17 views

### Observing charge from non inertial frame

Charge radiates EMW when accelerated. But what if we are in non inertial frame and observe charge. Does it still emit EMW. (Another question: do we observe the magnetic effects of a rest charge if we ...
10 views

### Why does mode is confined to higher index material in the waveguide cross section?

I know the EM mode is confined to higher index material and its result can easily be seen after calculating the eigenmode within the cross-section of the waveguide. But having trouble to understand ...