Em Definition and 1000 Threads

Hello all! I am trying to understand ER on a more intuitive level. I can see the relationship between energy and frequency. The relationship between amplitude and photon number is less clear. So far I have E = hf. I understand that the intensity of light is a function of the number of...

I'm reading my course book on ELectromagnetism and it is talking about a wave moving in the y-z plane but with polarisation in the x-direction, and it says that the equation $$\mathbf{E}=E_0 2i sin(k_0 z\ cos \theta) exp[i(k_0 y\ sin \theta - \omega t)]\mathbf{e}_x$$ Shows that there is no...

Visible light propagates at less than c in water. What about other wavelengths of EM? Do they all travel at the same reduced speed? I think not, but am not sure. If they travel at different speeds then Suzanna can be seen comin' round the mountain in certain wavelengths before others.

Hey all. I don't really understand how the fields of an EM wave have a vector. I think I understand the vector of a static EM field, but I'm having trouble understanding it when it comes to an EM wave. Could someone help me out a bit? Thanks. (I'm sure it's something simple that I just don't...

Consider a lens of diameter d and a focal length f >> d. Let the cross-section area of the lens be S = N*λ^2. Let a plane wave be focused from S to an area S1=λ^2. Then, by the linear superposition principle the electric field intensity in the area S1 will be N times greater than it was in...

Hi all, So quarks are given fractional charges, which then add to the total charge of the particle they constitute. My question is if the electromagnetic forces between quarks are taken into account? I was thinking that such things might be automatically taken care of via Feynman diagrams...

If photons emit virtual gravitons (but gravitons don't emit virtual photons) why isn't gravity considered to be a more fundamental force?

i was studying incidence of EM wave at a plane dielectric boundary and encountered equations in the attachment . I just want to know if n2 > n1 then electric field amplitude at the boundary increases . So from where does this extra value comes ? n1 and n2 are intrinsic impedances of 1st and...

How are stellar EM radiation formed?? I've read this in many books and sites... Any object above 0 K will emit EM radiation of all wavelengths... Now this is confusing me a lot... I mean, how for example a sun emit wavelength s of a Radio and it is the same sun which emits ultra violet and...

Hello everyone! This is my first posting. According to Maxwell, an accelerating charge emits a EM wave. All the books I have referred to, talk about the frequency of oscillating charge. How can we determine the frequency of EM wave emitted by a charge that is accelerating linearly? Thank you...

Hello, I have a question about the charge, q, that appears in, say, Coulomb's Law, Lorenz Force, etc. Can you use the charge associated with various ions? Say I wanted to find the force on aluminum by fluoride (I don't know why, those are just the first two off the top of my head)...

I understand that em radiation (light) will be produced if you cause a charge to oscillate. Does this happen at all frequencies? If I charged a comb by running it through my hair and then shake it up and down, am I sending out light waves?

I read that speed is directly proportional to wavelength in a medium. so does it mean that gamma is the slowest in air compared to the rest of the waves?

Is it possible (and practical) to use electromagnetic waves to heat copper (or other metals such as iron, steel or an aluminium alloy) over long distances (such as 1km)?

Homework Statement I'm given a charge density rho (\rho (r) = r^2 \sin ^2 \theta e^{-r}) and I'm asked to find the multipole expansion of the potential as well as writing explicitely all the non vanishing terms. Homework Equations Not sure and this is my problem. The Attempt at a...

I was wondering, if two EM waves of the same freq could add via superposition ON THE SAME ELECTRON or atom (at the same time) to become ionizing? For argument's sake say if each wave was just below UV I remember E = hf, which would indicate no, I don't see how the energy would not add...

Hi! Does electromagnetic waves induced emf or current in the coil or inductor due to faraday law as the magnetic field is continously changing in em wave?

According to this review: http://lanl.arxiv.org/pdf/quant-ph/0508202v1.pdf A classical EM plane wavefunction is a wavefunction(in Hilbert space) of a single photon with definite momentum(c.f section 1.4) , although a naive probabilistic interpretation is not applicable. However, what I've...

Homework Statement Consider 2 conductor hollow spheres that share the same center, of radii a and b (a>b). The hollow sphere of radius b is at zero potential while the hollow sphere of radius a has a potential of the form V(\theta, \phi ) =V_0 \sin \theta \cos \phi. Where V_0 is a constant and...

Why is it that a radio wave or a microwave is not affected by a magnetic field from a electromagnet or bar magnet? I know they are self contained and so no outside force should effect them but that I can't get my head around. The idea I have is that since the Electromagnetic field is...

A plane wave normally incident onto a perfectly conductive surface moving in the normal direction with constant velocity comparable to the speed of light. How do I solve such problem? If I treat the conductor as static, and the source of plane wave as a moving source, do I only need to consider...

We all know that the wave vector of a propagating plane electromagnetic wave indicates the direction of propagation. What does it mean by the "in-plane" wave vector of that plane wave?

The continuous version of the Lorentz force is \mathbf{f}=\rho\mathbf{E}+\mathbf{j}\times\mathbf{B} but what does f mean? In the discrete version F is the force on the charged particle appearing on the RHS. So if x is the position of the charged particle we have that its equation of...

I know that if you have alternating current in a wire, it will produce electromagnetic waves since the electric and magnetic field change direction continuously as the wave propagates, and that the wave direction, orientation of the E component, and orientation of the B component will all be...

My M.S. school is using Schwartz for EM instead of Jackson. I've heard horror stories about Jackson so I'm very happy at this news right now. However, does this mean I'm "missing out" and would need to do Jackson for a 2nd round of EM if I were to go to PhD in Physics at a different school that...

Have viewed PF, first time post (have searched for this question on forum): The energy of EM radiation can be described by the Poynting vector S = E x B (insert conversion factor for cgs, MKS, etc). For a traveling EM wave, what happens to the instantaneous value of S when E and B are...

Homework Statement It's example 3.8 in the Griffiths book in case someone has it. Basically the problem involves a uncharged metal sphere in a uniform field in the +z direction. Naturally, there will be induced positive charges on top and negative charges at the bottom. The question asks for...

I was wondering whether, making a comparison between the propagation of electric current through a conductor and the propagation of an electromagnetic wave through a dielectric, one could establish the following correspondences: Ability of a material to facilitate the propagation of the...

Hello, I have a loop antenna I have been messing around with for a few years and I understand most of the physics behind it, especially with regards to Faraday's Law of Induction; however, I'm trying to work backwards now to determine a source voltage at a distance. For example, if a...

All: This is a weird question. I'm trying to find a video or TV program, I'm hoping someone else saw this and can tell me what it was. There was a mouse or frog in a box or cylinder. They were experimenting with EM fields, very high energy and they were shaping the fields. I think this...

Given $20$ pairwise distinct positive integers each less than $70$. Prove that among their pairwise differences there are at least four equal numbers.

Homework Statement The electric field of a spherical electromagnetic wave in vacuum can be written in the form of: E(r,θ,phi)= A(sin(θ)/r)*[cos(kr-ωt)-(1/kr)sin(kr-ωt)]phi Show that E is consistent with ALL of Maxwell's equations in vacuum and find the associated magnetic field...

Hello! My book here states that for a medium where the index of refraction n increases with increasing frequency (or wavenumber), "the group velocity is less than the phase velocity". This is stated for a wave which is the sum of two waves with equal amplitude and differing frequency...

Derive the relation Δn.Δσ ≥ 1/2 where n is number of photons in an EM field and σ is phase Using heisenburgs uncetertainty principle? Tried subbing in frequency into heisenburgs uncertainty principle to get to the number of photons and to get rid of mometum is this the right line? Dont...

Homework Statement You and a friend are sitting in the outfield bleachers of a baseball park 140m from homeplate. The temperature is 20*C. YOur friend is listening to radio comentary with headphones while watching. There is a microphone located 17m from home plate to pick up the sound as the...

What is the difference between classical EM at the undergrad and graduate levels? Is it just the math that's harder at graduate levels, or are there any new concepts that are not covered in undergrad, that's covered in graduate? Thanks.

Homework Statement A point charge q is a distance a>R from the axis of an infinite solenoid (radius R, n turns per unit length, current I). Find the linear momentum and the angular momentum in the fields. (Put q on the x axis, with the solenoid along z; treat the solenoid as a nonconductor, so...

OK, so i understand that wave functions have something to do with something...i'm clueless, please help on this one. First, what ARE wave functions? i haven't an answer that i can understand, explain this to me dumbed down please. Second, what do they do exactly in the double slit...

I am assuming the answer to my question is no, but what am I missing? My reasoning is very basic: E=hf, therefore as the universe expands the wavelength of all the far traveling radiation is increased and due to constant velocity c their frequency must decrease which translates into them losing...

Homework Statement See figure attached. The file attach isn't working so here is a link to the problem statement, http://imgur.com/FhoIe The answer is given in a red box. Homework Equations The Attempt at a Solution The file attach isn't working so here is a link to my...

If you go to the relativistic Hamiltonian, what allows us to go from \dot{\vec{P}} = - \frac{\partial \mathcal{H}}{\partial \vec{x}} = e (\vec{\nabla} \vec{A}) \cdot \dot{\vec{x}} - e \vec{\nabla} \phi to \frac{d}{d t}\left(\frac{m \dot{\vec{x}}} {\sqrt {1 -...

In a single photon at a time double slit experiment. Is it the wave function or electromagnetic wave of a photon that is interfering? If both, what is the contribution of each? Remember that the electromagnetic wave is not the wave function of the photon. In a single photon, it has wave...

So, I have been doing a lot of reading. I have an 8 year old girl that has renewed my interest in physics, chemistry, biology, etc. I find it interesting that we say that Electromagnetic Waves travel through a vacum. We know that mechanical waves like those propagated in liquids and gas...

Hello all, I'm curious as to the opinion of some people here about what is more important: Complex analysis or EM II for someone interested in going into theoretical physics (mainly particle theory). I have a hectic workload for next semester. I'm taking particle physics, EM II, grad...

Hi, I have a question about destructive interference. Suppose I have two very closely spaced EM sources, e.g two RF emitters. At a point far away from the sources the arbitrarily orientated magnetic field due to source one is: B1(t)=sin(ωt) and source two: B2(t)=sin(ωt+pi) so the total field...

Is this the correct form for a Dirac electron in a Higgs field with scalar potential \phi and an electromagnetic field with vector potential A_\mu i \gamma^\mu \partial_\mu \psi = g \phi \psi + e \gamma_\mu A^\mu \psi where g is the coupling constant to the Higgs field and e is the...

My bad for the spelling fail in the title. Homework Statement I am utterly confused with the mathematics in a section of my notes, I swear that it's wrong - and it related to a piece of homework which I cannot understand. The electric field vector in a z-directed monochromatic EM wave is...

For censored data. Random sample X1,...,Xn Censored such that x1,...xm are observed but xm+1,...,xn are not - we just know they exceed T. fx = exponential = theata exp(-theta.x) L = ∏ (from 1 going to m) f(x;theta) ∏ (m+1 - n) 1 - F(T;theta) Using F = int f I get L =...

So I'm trying to understand how the Higgs field and Higgs boson are different from the EM field and the photon. Firstly how I understand the photon is that It is the quanta of energy that an electromagnetic field oscillating at a certain frequency can give to some other system. The photon is the...

I have known for many years that the speed of sound (usually quoted ≈340 m/s) and the speed of light (usually quoted ≈3*10^8 m/s) are vastly different. Doing some reading, I would seem to conclude that part of the reason for this is the fact that sound is a mechanical wave, propagated through...