Em Definition and 1000 Threads

Homework Statement Homework Equations <S>=c \epsilon E2/2 \Delta P = A \Delta t <S>/c The Attempt at a Solution My question is if we need the "box height"? This is my work which I'm assuming is wrong. :CIf there's another problem like this on here please put a link. I didn't see any, but...

Does the phase between electric and magnetic waves of light change if the path is bent by gravity?

I have recently studied about relativity being the reason for magnetism. The example given was about a magnetic field generated from current down a long wire. When two such wires with current in the same direction were parallel to each other there was an attractive force between them because...

Hello, I have derived two Maxwell's equations from the electromagnetic field tensor but I have a problem understanding the second formula, which is: \partial_{\lambda} F_{\mu\nu} + \partial_{\mu} F_{\nu\lambda}+\partial_{\nu} F_{\lambda\mu} =0 I have a few questions to help me start: 1) Is...

In special relativity, the electromagnetic field is represented by the tensor $$F^{\mu\nu} = \begin{pmatrix}0 & -E_{x} & -E_{y} & -E_{z}\\ E_{x} & 0 & -B_{z} & B_{y}\\ E_{y} & B_{z} & 0 & -B_{x}\\ E_{z} & -B_{y} & B_{x} & 0 \end{pmatrix}$$ which is an anti-symmetric matrix. Recalling the...

So in conductors, the electrons will distribute themselves to the surface via repulsion forces. But why do we say that the electric field inside is zero? If I put a positive charge inside, clearly it will move in some direction from the electric field of generated from the electrons. Also, are...

Hi, I'm taking an undergrad course in Electromagnetism and Optics, and in the lecture notes it reads: "Consider the formal equation ε0D⋅E = 1 ... that must be obeyed for waves traveling in different directions as defined by the wave vector k but with a given energy density." Could anyone help me...

Can the temperature of an object be derived from the EM Waves it emits? I know that everything having a temperature over absolute zero emits thermal radiations. The hotter the object gets, the higher the frequency of the wave goes. But for example if I have a hammer which emits a wave xHz...

Hi everyone, As we move from left to right in EM spectrum the energy EM wave carries in creases as does the Frequency. Then why even after having a lot of energy waves can't penetrate hard me trials like rock. For example, Microwave aren't that good in penetration of tough objects but have...

The following question/thought experiment is based on the dual nature (particle/wave) of electromagnetic radiation. Consider the emisson of a single photon on a 3D grid along the x-axis with its origin at (0,0,0). The only matter in this experiment consists of “electrons” found only in...

What is it about the em waves that get absorbed by electrons compared to em waves that traverse solid material.What is it about that wavelength, or frequency of light, and other em waves that get absorbed by electrons, that makes visible light get absorbed by electrons. Why that specific...

Hi, I am writing an essay for my extended project A Level, and part of this I am writing about the EMDrive. I thought I would be able to skim over how it works mostly earlier but have decided I would rather not. I am struggling to understand how it works and any explanation would be helpful. To...

Homework Statement [/B] Show that in order for the free Lagrangian to be invariant when ## A^\mu ## is transformed by a transformation U, it has to transform as below: ## A'^{\mu}=\frac i g (\partial^\mu U) U^{-1}+U A^\mu U^{-1} ## Homework Equations [/B] The wording of the problem is a bit...

Although mass-less, a photon, like any other quantum particle, has a frequency/wavelength associated with its energy/momentum. If we have a group of photons all with the same specific energy, then each photon can be represented by a little, complex-valued plane wave. Photons are also EM waves...

I know for sure that being familiar with vector Calc, multivariate Calc, and special relativity is helpful. What I mean by prerequisites is anything that would be helpful to know. For example, a textbook may include an appendix, or chapter on the mathematics required, but I'd much rather learn...

Homework Statement A plane electromagnetic wave is incident on a material surface. The wave delivers a momentum ##p## and energy ##E##. Then which of the following is/are correct? 1) ##p=0,~E=0## 2) ##p\neq 0,~E=0## 3) ##p=0,~E\neq 0## 4) ##p\neq 0,~E\neq 0## Homework Equations None The...

A comment a lab script for a recent experiment I did noted that the mechanism by which reflection of EM waves occurs is through the induction of Hertzian dipoles in a material. Having read up on Hertzian dipoles, I have found nothing which discusses them in the context of reflection. I read...

Guys, I am studying about electromagnetic waves and I'm not able to differentiate between a photon and a em wave or I'm not understanding it. Please help me to solve it out. Thanks

Book says one of the properties of EM waves is they can impart momentum (and angular momentum)... What would be an example of this? (a simple example in terms of first year physics i mean)

In a vacuum, the plane wave solutions to Maxwell's Equations are... E=E0*cos(wt-kr) B=B0*cos(wt-kr) ie they are in phase. (See for example https://www.physics.wisc.edu/undergrads/courses/spring08/208/Lectures/lect20.pdf http://hyperphysics.phy-astr.gsu.edu/hbase/waves/emwv.html ) I don't...

Hi, I was able to correctly calculate the answer to part 1 below but the answer to part 2 is incorrect and I cannot see the error of my ways... any help gratefully received. 1. Homework Statement An electromagnetic wave has an intensity of 127 W/m2. 1) Find its rms electric field strength...

Homework Statement EM wave with circular polarization travels in directon z interferes with perfect conducting surface xy. 1. find reflected wave 2. calculate induced charge density and surface current induced on conducting surface Can you verify if I started point 1. correctly, and give...

Homework Statement In a region of empty space, the magnetic field is described by ##\vec{B} = B_0e^{ax}\sin{(ky-\omega t)} \hat{z}##. Find the speed of propagation ##\vec{v}## of this field. Homework Equations ##\Delta \vec{B} = \frac{1}{v^2}\frac{d^2\vec{B}}{dt^2}## , ##k=\frac{\omega }{...

I wanted to know if my reasoning is considered sound, and if not please tell me the loopholes you can observe. The energy density in an EM field is (Its not necessarily a plane wave we're talking about here). ##u= \frac{\epsilon E^2}{2}+\frac{B^2}{2\mu} ## The relationship ##E=cB## is...

Maybe a stupid question and maybe sensless to ask, but as I don't know, I ask anyway: what is the length of the newly found gravitational waves in terms of traditional EM wavelengths?

Matter has a wavefunction associated to it. But what about light? Does it have both a electromagnetic wave described by Maxwell's equation and a wavefunction described by Schroedinger's equation? Or is the electromagnetic wave considered to be the wavefunction of the photon? I read somewhere...

-iation. Could the opacity of a material to one band of EM radiation (light) could be altered by irradiating the material with another band of EM radiation (X rays)? I think you are suggesting that: By raising the electrons in the atoms to higher energy bands (with the X rays), so that they will...

Hi. Charge is one of the few properties a black hole can have. EM interaction is mediated by photons. How can they escape the BH?

Hi... If we consider propagation of sound through a medium other than vacuum, we mean, when sound is produced by a vibrating speaker diaphragm, it gives periodic jolts to the molecules and atoms present in the medium or air. These "pushes" are transferred to all adjacent atoms until finally few...

If I use 10mm (thickness) of a metal for the sides of a Faraday cage, with a 5mm skin depth at the frequency to be shielded, & increase the v/m of the EM wave to be blocked gradually, will there be a stage where the skin depth will increase to 6mm, or is 5mm the maximum limit?

Does an accelerating charge, such as one turning a corner emit an em wave or just a pulse? Classical logic dictates it should just be a pulse as there is no oscillation. But which is it?

What sort of EM field is produced in an induction heater? And how to measure it? That's it, basically. Assuming an induction heater is running on 200khz, and consuming about 3000 watts, how would I go about measuring the magnetic field produced in its coil? Now, I'm rather confused about all...

Why can't we have an Electromagnetic wave in which the Electric Field and Magentic Field aren't in phase?

I just had a flashback to an applied electromagnetic course I took a few years ago. I believe we were learning possibly about waveguides (maybe) or something, but there appeared a phenomenon in the math that made it appear as if the wave was traveling faster than C. When asked about it, the...

In electromagnetism we have these two Lorentz scalars: ##P=B^2-E^2## ##Q=E\cdot B## WP https://en.wikipedia.org/wiki/Classification_of_electromagnetic_fields claims that these are a complete set of invariants, because "every other invariant can be expressed in terms of these two." How does...

How do you treat decoherence in purely electromagnetic field? In other words, can EM field also have decoherence? How?

we use perfect fluid which is characterized by a energy density and isotropic pressure for general forms of matter. When guessing the values of energy momentum tensor indices we can use the physical insight that they are the flux of four momentum in a constant surface of spacetime. The...

How would you calculate the energy in an electromagnetic field produced by a particle such as an electron?

Electrons have both mass and electromagnetic charge, so why is it that an electron's rest energy is equal to its mass energy with E=mc^2? Shouldn't it have some energy left over to excite the electromagnetic field? The mass energy excites the Higgs field, so why is there no energy for the EM field?

I know there is a pi phase shift when going from an area of lower index of refraction to higher. Is this phase shift still pi when going from a non-conducting dielectric with index of refraction n and reflection off a "good" conductor?

Hey all, is there a formula that can calculate the energy losy by a photon traveling through air at 1 atm per meter given frequency? Any help apreciated.

So its been a while since I studied maxwells equations, anyway: So From my ignorant perspective, trying to derive conceptual meaning from these, I can see that the time dependant study there is some conductivity x the partial differential of the magnetic vector potential plus the cross product...

Homework Statement I am just wondering is there any apparatus available to produce EM waves of arbitrary wavelength and intensities? If not, how I can produce an EM wave of my desired wavelength in the laboratory? Homework EquationsThe Attempt at a Solution I completely have no idea :(

I tried googling a good resource for this but it was difficult to think of good keywords. Are we always allowed to do this, or is it just for plane waves, linear media, conductors, etc? My intuition is that it's fine in all circumstances since we can Fourier decompose most any function into...

Is there any star systems (planetary) that are influenced by the EM Force, hence as usual,sum of the charges of elements in the universe are electrically neutral.

I've heard the claim that the gauge freedom of the general Lagrangian can be used to derive the Lorentz force on a charged particle. I understand that Langrangian gauge freedom allows A⋅v -∇φ to be unaffected by the gauge freedom in defining the EM potentials, but this seems like a convenient...

If photons are the force carrier of the EM force, and they have no charge, how do they give the information between two charged particles? How would a proton know the difference between a electron and positron?

I think the equation for the relationship of the E (electrical) and B (magnetic) fields in electromagnetic (EM) radiation is E=Bc, where c is the speed of light. I think this is correct, but what does it tell us? On it's face, it looks as though the B field (of a photon, say) is...

Homework Statement Suppose we have a infinite cylinder of radius=R and with uniform volume charge density ρ. Use Maxwell's Equations or relationships from them to find E, B, V, and A everywhere. Pretty easy. But how do you approach the problem when you bring an angular vel into the mix...