Em Definition and 1000 Threads

1. Since skin depth is the attenuation of the wave in a conductor, this means the reflection isen't the incident wave... so what is the reflection? 2. Water doesn't stop light since it's frequency is too high, i saw on forum it's because the big ions can't move fast enought. How can that be...

Hi guys. I play now a bit with EM fields and I have encountered some problems connected with Dirac delta. By coincidence I visited this forum and I thought I could find some help in here. The problem is that in order to get a potential in some point from a single charge you need to just...

Hello everyone! Let me first say how cool it is that this forum exists, I wish I'd thought of coming here years ago. I am trying to understand how EM radiation works. From the high school physics that I've learned I have been under the impression that reflection was due to electrical...

Hi all, I was reading "Geometrical Optics Reflected Fields" chapter from "Introduction to Uniform Geometrical Theory of Diffraction" textbook. The author assumed that the surface is perfectly conducting and therefore he only considered the reflected waves. He derived a formula for the...

Homework Statement Two incoherent EM waves of intensities 7I0 and 13I0 travel in the same direction in the same region of space. What is the intensity of EM radiation in this region? Homework Equations The Attempt at a Solution I have tried using I = I1 + I2 + ( 2* square root of...

I am trying to understand why it is not possible to produce an EM wave through interference that is completely different from the source waves. For example why can't 2 or more EM waves outside the visible spectrum add up to produce light? I haven't had any physics since high school and I don't...

We know that in electrodynamic when an incident Electromagnetic wave strikes a charged barrier it can either be reflected or transmits. And both of the incident, reflected and transmitted waves are in the same plane called plane of incidence. Now, i met a problem in which they state that the...

Homework Statement The E field in an EM wave has a peak of 22.8 mV/m. What is the average rate at which this wave carries energy across unit area per unit time? Homework Equations S = e_0*c*E^2 The Attempt at a Solution where e_0 = 8.85*10^-12 c = 3*10^8 E = 0.0228 V/m S =...

This isn't a homework question so much as a general question about the equation I see used in the textbook: The E field of an EM wave is defined as E(x, y, z, t) = E0sin(kx - wt)y_hat and the B field of an EM wave is defined as B(x, y, z, t) = B0sin(kx - wt)z_hat. Why is there a minus sign...

Does it removes either the electric wave of magnetic wave component of the EM wave? And if so, won't the wave exiting the polariser not a EM wave anymore? More like an E wave or M wave. If the above argument is correct, won't the speed of light become\frac{1}{\sqrt{\epsilon_{0}}} or...

Hi ! I've a question. Where is the connection between the (kinetic) Lagrangian - \dfrac{1}{4} F_{\mu \nu} F^{\mu \nu} and a plane wave of the form \vec{\varepsilon} exp(i \vec{k} \cdot \vec{x}) / \sqrt{V} (the epsilon is a polarization vector) confined in a box with a finite volume V ? I...

I know that a charged particle emits photons which are the "carriers" of the electric and magnetic fields, and that these photons, interacting with another charged particle, cause an attractive force or a repulsive force. I also know that examining the amount of energy in the photons - which...

Hello, The city added a new electric transformation station near my house and has recently closed down a kindergarten adjacent to it due to 'radiation safety' reasons. My house is two doors down and my mother is concerned that radiation from the station might be hazardous to her health. She...

I want to know how to find the electromagnetic field at a given point around a moving charge and this has led me to a few questions. My first one is, do both the \mu _0 \bf {J} term and the \mu_0 \epsilon _0 \frac {\partial}{\partial t} \bf E term contribute to the...

Homework Statement Hi, I've attached the question as I don't know how to write equations on here without them looking awful.Homework Equations Laplace -> del^2 V=0The Attempt at a Solution I've done the first bit (expression for Q0). For the next bit I tried to solve laplace's equation to find...

To star this post off, I would like to say that I am in not an expert in any field of physics but I do have an interest. So, my question is... Can the human body produce an EM field that is strong enough to affect electronic devices? Examples. computers- I'm pretty competent with them...

Homework Statement A certain star is 13 million light-years from Earth. The intensity of the light that reaches Earth from the star is 6 10-21 W/m2. At what rate does the star radiate EM energy? Homework Equations i know you have to convert lightyears to m. (1.23e17m) multiply this...

Homework Statement How much energy is transported across a 1.15 cm^2 area per hour by an EM wave whose E field has an rms strength of 36.5 mV/m? Homework Equations E=hv? The big problem I'm having is that I don't know what formulae to use. The Attempt at a Solution I know what V/m...

Hi Friends, I am an undergrad currently taking my first course in particle physics. In thinking about various possible reactions, I have run across what appears to be a rather basic question: Why are reactions of the form e^- + e^+ \rightarrow \gamma \rightarrow q + q^' where q and q' are...

Are there any EM wave behaviors that cannot be explained in a purely physical, "photonic" manner? I'm speaking specifically of the photon's path from emitter to absorber, irrespective of "why" that path was taken (in other words, the double-slit experiment does not qualify in the context of my...

isnt the field in any given volume always uniquely determined to prove by contradiction assume E1 and E2 div(E1)=charge density/epsilon 0 =div(E 2) by fundamental theorem of divergences integral of E1.da = integral of E2.da over entire surface thus E1=E2 then why does griffith in his...

Hello, I am having trouble seeing how to derive the energy equation for a charged particle from the equation of motion. The equation of motion is m\frac{d\bar{v}}{dt}=q(\bar{E}+\bar{v} \times \bar{B}) Then in the notes I have it says "projecting the eq. of motion onto the particles...

I have been desperately trying to find an equation (or a set of equations where I can derive an equation) that shows a relationship between the energy in an electric field and the wavelength or frequency of an electromagnetic wave. I am trying to show a relationship between Wavelength and...

Consider please that an observer is located in a plane sinusoidal and polarized e.m. wave. He erects a metalic antenna normal to the direction of propagation. A sinusoidal potential difference appears between the two ends of the antenna having the same frequency as the e.m. has. Is that a...

I am studying EM wave and transmission lines. I see both derive equations for propagation constant \gamma: Plane wave velocity is 1/\sqrt{\mu\epsilon} and \eta = \sqrt{\mu/\epsilon} Transmission line velocity is 1/\sqrt{LC} and Z0=\sqrt{L/C}. From that the book just to say the velocity...

I am trying to review some basic physics, purely for my own interest, and have been looking at particle physics in the form of the Bohr model and EM theory in the form of Maxwell’s equation. While I still have a way to go on these topics, I was wondering if anybody is in a position to help me...

Show that the electric field: E = Emsin(kx-ωt) and magnetic field: B=Bmsin(kx-ωt) satisfy the following equations: -\frac{\partial B}{\partial x} = \mu_{0}\epsilon_{0}\frac{\partial E}{\partial t} and \frac{\partial E}{\partial x} = -\frac{\partial B}{\partial t} I have no idea...

Homework Statement this integral owned me, can anyone tell me what to do to solve it/ how to solve it or a step by step solution. from 0 to h, 1/((h-r)^2+r^2))dr Homework Equations The Attempt at a Solution Im thinking partial factions or trig sub...

Hey all, I am an undergraduate taking a particle physics class and we just learned that the EM force was caused by charges "spitting" virtual photons back a forth. In like second grade we learned that the EM force was dependent on the two charges involved (keeping this simple) and the distance...

Round em up, send em to GITMO! I'm watching CNN and YET AGAIN another CEO is spending wild sums of money (1.3 million) to redecorate his office. He spent 14k on a waste basket. Over and over, all these CEOS are scum bags. I mean jesus christ, how disgraceful.

Anybody knows if there is a rule for EM radiation cross over materials ? The wavelenght in comparison the size (or structure) of molecule is determinant ? Ex. why infrared pass through the concrete but not metalics ? Thank you.

Hi I hope this is the right place to post. I have some questions regarding EM wave amplitudes. There are some other posts in the past regarding this and some people replied by saying that amplitude of a light wave is equal/close to wavelength of the wave. This is deduced from the fact that...

I know that in free space, the general solution of the wave equation about electric field is of sine and cosine form. One can also write it in complex form as E = E_0 \exp(i\vec{k}\cdot\vec{r} - i\omega t) I have two queations about this solution 1) If consider the polarization, how...

I love Star trek and I was thinking, how to create a warp drive. I have read a discusion about EM waves on this forum, there was written that they do not need any medium for propagation and : “In a simplified sense the oscillating E field sustains the oscillating B field which sustains the...

On the boundary (surface) of two regions, the tangential components of electric fields on above and below surface are continuous. I wonder if it is also true for displacement \vec{D} and polarization \vec{P}? That is, can I say: the tangential component of \vec{D} or \vec{P} on above and below...

In EM wave polarization. Where is linear polarization where \gamma =0 or \pi . \gamma = +/- 45 deg and amplitude of Ex and Ey are equal to give circular polization etc. My question is why there are different angle of \gamma on the first place? If you set the reference at x...

Speed of EM travel through the good conductor is \omega/\beta I know the speed of signal travel in stripline is c/\sqrt{}\epsilon_{}r_{} My symbols don't look very good but I think you get what I mean. Obvious they are different. I am confuse because in both case EM wave travel in good...

Alright first time poster here with a question that has been eating at me for a while. I am curious to know if there is a substance that when one part of the EM spectrum is passed through it, it would come out as another. I know that if you are to shine a lightbulb on some black cloth you would...

I am trying to derive the electromagnetic wave equations from Faraday's law of Induction, and the Ampere-Maxwell law. But, I am having a problem with the 1/c^2 disappearing. This is what I am using: \nabla\times\vec{B}=\mu\vec{J}+\mu\epsilon\stackrel{\partial\vec{E}}{\partial t}...

Homework Statement 1. The expression F = [x,y,z] defines a vector field. Given the parametric representation of a surface S:[u cos v, u sin v, u^2] = r (u,v), where the parameters cover the ranges 0 ≤ u ≤ 2 and 0 ≤ v ≤ 2π, calculate the flux F through the surface S.Homework Equations How do i...

Homework Statement Find the velocity of EM waves as a function of \epsilon_{0} and \mu_{0} 2. The attempt at a solution E = E_{0}cos(kx-\omega t) Using v= \frac{\omega}{k}

I know undergrad QM fairly well. There they use the EM potential to introduce EM fields into the momentum. What should I study to understand the connection between EM fields and actual photon particles?

The maximum I have found about contact force is very roughly this: it is nothing but electromagnetic force, meaning that, if two bodies collide, the electrons of the atoms of the outer shell of each body repel each other, those atoms displace towards their neighbours and repel them in turn, thus...

Homework Statement Sketch in 3D, the following waves. (both E fields are in x direction E_1 = 3*exp(-j*8*Pi*z) E_2 = 4j*exp(-j*8*Pi*z) (where j=sqrt(-1)The Attempt at a Solution I know how to sketch E_1, but my question is how to treat the imaginary amplitude, 4j in E_2. here is my stab at...

Hi, i am working in a motion capture project one of its parts is a sensor i need a formula of the voltage generated in the coil due to moving in electromagnetic Field from an inducer i think it depends on ( B , cosθ , µ , N , L , r ) i post this thread in another forum but no one answer...

Homework Statement Basically, the problem states that a cavity at temperature T is emitting EM waves isotropically in all directions (with frequency distribution of Planck's Law). If the time averaged density is <e>, find the value of d<S>/dw where w is the solid angle and the quantity is the...

Does a stationary charge emits electromagnetic radiation? Does a moving charge in magnetic field emits electromagnetic radiation?

Homework Statement Difference between EM wave & a Matter wave ?

Hi all, I have brave hopes of modeling the following problem: Imagine an antenna transmitting an ~50V 100kHz sine wave. Imagine a receiving antenna placed three or four feet apart, with an amplification and detection circuit. First, measure the amplitude of the received wave. Next...

I've been trying to obtain the EM stress energy tensor... but I'm not sure if what I got is correct. In all the websites I googled, I found T^{\mu\nu} =- \frac{1}{4}g^{\mu\nu} F^{\alpha\beta}F_{\alpha\beta} + F^{\mu}\,\!_{\lambda}F^{\nu\lambda} However, is this with the sources or without...