Em Definition and 1000 Threads

Today, I made the following question at Physics SE, but the community redirected me here In short, I have made a proof for EF/MF phase difference near an oscilating dipole that "vanishes" far away from the dipole. So, what I am asking for is a proof verification. The physics SE post...

Homework Statement Consider a particle of charge q and mass m , free to move in the xy plane in response to an electromagnetic wave propagating in the z direction. Ignoring the magnetic force, find the velocity of the particle, as a function of time. Assume the average velocity is zero...

Why is gravity not electromagnetic radiation like attractive/repulsive force? I know the ans is related to shielding but I don't get it.

An article in Wikipedia tries to explain pigments. One particular section has the following: "A wide variety of wavelengths (colors) encounter a pigment. This pigment absorbs red and green light, but reflects blue, creating the color blue." Questions arise... They may see stupid, but please...

Homework Statement I am trying to use Zangwill's book to calculate the transmisson (T) and reflexion (R) coefficients for an EM plane wave going through 3 layers. (the intermediate layer has a width d). I am reading pages 604/605, he defines "N+1" as the number of layers in which layer 0 is...

I started out with a video of someone "measuring" the speed of light by microwaving a chocolate bar. Not surprisingly, this turned out to be partially bogus. http://morningcoffeephysics.com/measuring-the-speed-of-light-with-chocolate-and-a-microwave-oven/ This sparked some more questions...

UV catastrophe didn't occur because em are quantized.. so the higher frequency modes were not there. In vacuum.. if you compute the contribution of the em modes, it is 120 magnitude greater than observed.. the mystery is why it is not and they theorize it is just canceled out. But why didn't...

Why are electric and magnetic fields in an electromagnetic wave in phase? Can somebody please explain that?

Why can't there be a term in the SM lagrangian for the U(1)_Y of the form: F_{\mu \nu} \tilde{F}^{\mu \nu} ? As there is for the strong interactions? (Although I've seen such terms appearing in the axion models, such as the KSVZ where by introducing an additional very heavy quark Q with...

QUESTION 1. I have asked this question here a while before but it seems that I have still not gotten it. My apologies to the previous answerers of this one, I guess it's just me being slow. We defined the electromotive force ##\epsilon## for a charge that moves along some path while some force...

Homework Statement Sphere of a radius R=50 cm is in nonmagnetic medium of permittivity ε=4. EM wave with amplitude of electric field Em= 200 V/m is spreading through the medium. How much energy pass through surface of sphere through 1 minute? I have couple of question here. Since the sphere...

My question relates to wave/particle duality. If light is regarded as possessing both wave like and particle like properties, and visible light is just part of the whole EM spectrum of radiation, is it correct to say that radio waves for instance, ( being themselves part of the whole spectrum...

It's kind of embarassing but I have almost finished a introductory EM class and I'm still not sure in a formal way in which cases the EMF is equal to the voltage. EMF was defined as the work done on a charge per unit of charge by any EM originated force when the charge would take a certain path...

Suppose we're given the action S=-mc\int ds + \frac{q}{c}\int A_{\mu}(x) dx^{\mu}-\frac{1}{4c}\int d^{D}xF_{\mu \nu}F^{\mu \nu} The first two integrals are over the particle's worldline while the last is over spacetime. So I'm able to successfully vary the action with respect to the gauge...

Homework Statement Given a uniform plane wave in air as: E_i=40cos(wt- Bz)a_x +30sin(wt- Bz)a_y (a) Find H_i (b) If the wave encounters a perfectly conducting plate normal to the z axis at z = 0, find the reflected wave E_r and H_r. (c) What are the total E and H fields for z < 0?Homework...

How high frequency makes waves dangerous for us.also does all em waves have same speed of light?

If we consider E and B individually, there are 6 total degrees of freedom. But they are actually related to each other by Maxwell's equations. So we can find potentials and reduce dof to 4; 3 in vector potential and 1 in scalar potential. Thus, there remain 2 redundant dof. This is the...

hi , what is the equation for the hamiltonian of EM field in dielectric and how can we say we have quantized the hamiltonian?

Radio or any other wave in electromagnetic spectrum? Sound perhaps? And at what frequency(ies)

explain this derivation: Source: microwave engineering, pozar Why did pozar use those conjugates? What does the source current mean?

I understand that reflection of EM waves is the electrons on the surface of an object being caused to oscillate, and transmission is the electrons all the way through the object being caused to oscillate. Why, in reflection, when the electrons on the surface of an object are caused to...

Hello. I was taught that a charge which changes its velocity must radiate (at least, in classical electrodynamics). Let's consider a charged particle which decays into another charged particle (and, maybe, others neutral particles; but not photons). In this case, can we find electromagnetic...

If I have a charge in a vacuum, and I accelerate it in a direction, then stop accelerating it, an EM wave will be produced for a short amount of time. How can you determine the frequency of the EM wave which is produced? Does it depend on the speed at which the charge moves? The amount the...

Do we say something is an EM wave only if the EM field is oscillating at a constant frequency? What exactly is the definition of an EM wave? If an electron moves in a direction and then stops moving, is an EM wave produced by that electron?

What experiments disprove the idea that light is waves of electromagnetic field?

EM field strength dies quickly with distance, what's so special about going up and down that allows EM waves to maintain their energy over infinite distance?

Is it one wavelength of EM wave? I have googled for this and I can't find an explanation for what a photon is in terms of EM waves.

For EM wave, magnetic and electrical components are in phase, meaning when E = 0, then B = 0. Thus, I understand if it is written: f(x,t) = A(cos(kx - wt) + icos(kx - wt)) Then why plane wave is always described: f(x,t) = Aei(kx-wt) = A(cos(kx-wt) + isin(kx - wt)) Implying that Real and...

I am not looking for formulas or references to theories... this is just a general question about how to visualize/explain EM waves. Are EM waves such as light, radio waves, etc. really more like pulses and we just measure their intensity from a static point as a wave line? I thought I...

If EM waves create gravitational field "around" them (as I understand is the case) which reference frame we should use? We could imagine several observers, some moving in the same direction with EM wave with different speeds, others moving in the opposite direction. The different observers...

Dear Forum, Vacuum is classically interpreted as the absence of everything. But the quantum view of vacuum sees it as a bubbling, dynamic entity from which particles and antiparcles emerge for very short intervals of time. Relativity teaches us that energy and matter can be converted into each...

Hello, I am reading a book about General relativity, i understand that energy of the EM tensor go in the stress- energy tensor of GR equations. SO, EM field curve space. But i don't understand if space curvature impact EM field ? Is variation of space curvature can create EM field ? Clément

A lot of electronic hobbyists would want to transmit information, signals through a medium other than the usual rope called wire or cables As this is a bit old fashion to have wires as a means of sending switches. So here let's share ideas on how to produce Electromagnetic wave... The only...

Hi all, I've got a quick clarification question. Generally when the production of electromagnetic waves are discussed, it's done in the context of an accelerating electric charge. Is it possible to generate EM waves by instead accelerating something like a permanent magnet? I.e. if I wiggle a...

Quick question. If the EM field vectors are perpendicular to the direction that an EM wave is traveling, how can light push objects away from the light source, such as in the use of a solar sail?

Hi, I have a few question about EM waves. What is an EM wave composed of? Are the E and B field lines real or imaginary. .. if it is an wave what is waving? (Eg water is waving in tsunami) wouldn't a pulsating chargr produce a electric pressure wave?

Consider the following experimental setup: the front half of a klystron tube (the electron gun and resonent cavity) or perhaps a free electron laser, several different targets consisting of a highly conductive(metal) object, a possibly conductive object(salt or clay), and a non-conductive...

Hello, I read the Feynman's QED book, where I learned that a photon has a intrinsic property called frequency. This property affect, for example, the interference profile when we have a lot of photon together. Ok. Now, thinking on an conventional antenna. When we have a 100kHz signal on...

I want to pump energy into a chemical species to increase its reaction cross section with another. Typically these species react upon collision when their relative kinetic energy exceeds the activation energy. I want to find a way to increase the reaction rate for interactions at slower...

Homework Statement I'm working on using the wave equation to prove that EM waves are light. Homework Equations Here's what I'm working with: E = Em sin(kx-wt) B = Bm sin(kx-wt) ∂E/∂x = -∂B/∂t -∂B/∂x = μ0ε0 ∂E/∂t and the wave equation: ∂2y/∂x2 = 1/v^2(∂2y/∂t2) The Attempt...

Hi I am re-reading Srednicki's QFT. In chapter 58, he points out that the Noether current $$ j^\mu=e\bar{\Psi}\gamma^\mu\Psi$$ is only conserved when the fields are stationary, which is obvious from the derivation of the conservation law. Meanwhile he assumes that $$\partial _\mu...

Homework Statement I uploaded a picture with the question Homework Equations my problem is : How should I find all the symmetries of the action ? Is there an easy way to recognize those symmetries or should I try all the symmetries I know and see if the action doesn't change...

Hello 1-here is a problem that want to specify which current loop has max electromagnetic intensity?(the correct choice is d) (Loop radius: small loop (r) big loop(2r)) so i think choice C is correct it because of this result and do i think correct or not? 2-for obtain...

Hey, I'm new here but I was hoping you guys could help me out. I am currently studying Waves mainly using MIT's course 8.03 - Vibrations & Waves. I am now at a point where I have almost finished reading AP French and entering EM Waves. Unfortunately French decided (for whatever reason) to not...

Hey all, Random question, but is there anyone in the microwave/radio frequency industry that also wonders the biological effects of constantly being exposed to it? From what I have been told, the effects are not scientifically sound, and as such, the majority of people I have met treat that...

Mechanical waves (sound, water waves) and EM waves both undergo diffraction. But the actual physical processes involved in the two are totally different. EM waves are produced by accelerated charges while mechanical waves are tiny displacements of molecules of the medium in which the wave is...

Do individual photons have some attributes which relate to EM wave frequency? In other words, is there any difference in photons composing a red and blue beam of light?

Why do parabolic reflectors for microwaves (e.g. satellite TV) not reflect light like a mirror? Why do things like spoons, which are presumably conductive, reflect light? Thank you

I saw an example of a hypothetical EM wave that had constant E and B fields. Is that possible? How would it be produced? And wouldn't such a wave have an infinite wavelength?

Hi, I've read that the speed of em waves in the vacuum is the electric field component frac the magnetic field component, why and how can this be explained more easily ? Thanks