Em wave Definition and 214 Threads

Hello , there is a polarization matix I want to implement in matlab. I have build a basic matlab plot which could visualize EM waves in 3D. The basic equations described in equation 2.5.1 from the attached link. given the simple case of linear polarization, What is the strategy of plotting...

( @jrmichler wrote to me: "SHEESH, more fearmongering. But please do not bring these conspiracy theories to PF." You write to wrong person, you and moderator of PF can send a email to scientists in WHO/International Agency for Research on Cancer (IARC) and ask them why they make this...

I'm posting this topic after an invitation to do so. So considering that transcranial magnetic stimulation which operates in frequencies and therefore through EM induction can excite neurons, then can an EM wave also excite neurons?

In Classical Physics, when a charged particle oscillates, it emits an electromagnetic wave, and the frequency of the wave depends on the frequency with which the particle oscillates. But in Quantum Physics, when an excited atom emits a photon, the energy of the photon depends on the amplitude of...

According to Maxwell’s Equations, the speed an EM plane wave in free space, far from its source, is determined by the electric constant, ε0, and the magnetic constant, μ0, such that c = 1/√( ε0 μ0). The units of ε0 are capacitance per unit length and the units of μ0 are inductance per unit...

Sometimes I cannot imagine light as the popular Maxwell's blue and red electric and magnetic wave https://simply.science/images/content/physics/Electromagnetism/em_waves/emv.jpg but I found the image below to be the more accurate representation of how light actually looks like as waves...

Let's say we have a point source of an EM wave in a vacuum of total energy E, and an absorber atom at some distance from this source, whose first excited state is at the energy B, with B < or = E. The energy of the wave is constant as a whole, but at each point around the source the energy...

A Ion source is a device that allows creating ion beams (e.g. argon ions) and to project them outside the device, for example to be further processed by a particle accelerator, or to irradiate materials or biological tissues etc. Now, suppose the ion beam is coupled with an EM wave, especially...

Hi alltogether, I have been confused about a certain topic of EM wave propagation: it´s clear to me that E and M field are perpendicular to each other (I know Maxwell´s equations well). But: sometimes you can find on the internet that both fields are in phase...

In classical EM, consider an EM plane wave traveling in free space. The ratio of the amplitude of the electric field to the amplitude of the magnetic field is the velocity of the wave, the speed of light. Is the above also true if the wave is spherical, expanding from a point source, as in a...

There is no possible measurement, no matter how clever, that can measure the one way speed of light. It is a synchronization convention. In this topic I would like to apply this idea on a specific case. I have a microwave oven with width L. In this oven I have a standing wave. $$E(t,x)=E...

Hi, I have an expression in my textbook that I don't really understand. I have 2 questions regarding this expression for a linear EM wave## \tilde{\vec{E_{0i}}} = (E_{0x} \hat{x} \pm E_{0y} \hat{y}) e^{i(kz- \omega t)}## ## \tilde{\vec{E_{0t}}} = (\sum_j E_{oij} e_{pj}) \hat{e_p} ## ##...

Hi all, as we all know EM waves are made up of magnetic and electric waves in a plane perpendicular to the direction of propagation. Given this, why don't I see conductors being affected when I shine light at them? Woulnt the magnetism cause a force? Is is that the force is too small? What am i...

1.) In electromagnetics, wavelength in a medium is $$\lambda = \frac{\lambda_{0}}{n}$$, where $$n$$ is the refractive index. What is the equivalent formula for sound wave in a medium? 2.) Is there a reference sound velocity, like electromagetic wave speed in vacuum is $$c_{0} =...

It is well known that one can solve incident an reflective wave in homogeneous linear media by matching PDE boundary conditions. In the electrical engineering community, one solves similar problem using smith chart and scattering parameters for 1-dimensional propapation of TEM modes in...

Why we know that average speed of a single photon(in point particle view) equal the speed of EM wave?If average speed of a single photon smaller than c then there exist massive photons?

As I learn in class, when EM wave goes from medium 1 to medium 2, there are 3 possibilities that can happen Totally transmitted (i.e when the angle of incident is 0 degree) Partially transmitted and reflected (i.e when the angle of incident is between 0 and critical angle) Total internal...

Hi, In Problem 9.12 of Griffiths Introduction to Electrodynamics, 4th edition (Problem 9.11 3rd edition), in the problem, he says that one can calculate the average energy density and Poynting vector as using the formula I don't really understand how to do...

Velocity of photon allways is c(photon is massless particle).While velocity of EM wave in medium < c.So does velocity of photon need not allways equal velocity of EM wave?

Is there an uncertainty between amplitude and phase in classical quasi-monochromatic light?(E(t)=a(t)cos(phi(t)-omega_0*t))If it exist, what is the relation between classical and quantum uncertainty(delta I* delta phi>=1/2)?

They say wave function is different to quantum field. Then what is the difference between EM wave and EM field?(By the way :Is that EM wave the wave function of photons?).It seem to me EM wave is the wave of EM field?

Hello there. I set up the problem like this, I have a wave incident from air on the anti-reflective coating consisting of: ##\tilde {\vec E_I} (z,t) = \tilde E_{0_I} e^{i(k_1z- \omega t)} \hat x## ##\tilde {\vec B_I} (z,t) = \frac 1 v \tilde E_{0_I} e^{i(k_1z- \omega t)} \hat y## This wave gets...

The energy density of an EM wave is given as (1/2) ϵ E^2 + (1/(2μ)) B^2. This is derived from the energy density of the electric and magnetic fields of capacitors and inductors, respectively. But why should the energy density of the fields of capacitors and inductors be the same as that of...

Let me ask a very primitive question. To and fro motion of pendulum under gravity tells us potential energy + kinetic energy = const. At the top points potential energy: max kinetic energy :0 At the bottom point potential energy: 0 kinetic energy :max EM wave is usually illustrated as...

we know that all emission from asctrophysical context is doppler shifted. So, how to make sure the doppler shifted 21 cm not contaminated by some other emission?

I've searched threads and can't find easy explanation - sorry if I'm missing something basic / have a basic understanding error! In the classic picture of an EM wave with the Electric and Magnetic components oscillating at 90 degrees to each other, both components cross the middle axis at the...

By reversibility, if we turn the direction of the light propagation by 180 degrees, then the new propagation path follows the old propagation path. I suspect that when there is diffraction, the light propagation is not reversible?

You don't have to read all this theory to answer my question. I added it just in case. Above they use the definition work energy theorem in vacuum to get to (8.12). Since it is in vacuum I would guess that one could use the equations for B and E field from EM-waves so that magnitude...

So, my game is coming along. My psychic energy shielding protects against EM radiation. The energy used for shielding gets depleted based on the type of EM radiation (the wavelength) and according to the amplitude of the radiation the energy shielding is exposed to. I can't find many numbers...

Does a single photon travel in two different waves at once? If photons are particles like the Photoelectric Effect, Compton Scattering, and Blackbody radiation all suggest, how do polarizing filters block light completely? Is a particle from a radio antenna actually that large in size?

For this question I want to clarify that 5k which is the electric field component perpendicular to the incident plane ( the xy plane) will be continuous for reflection and refraction , For which none of the options seems correct ,am I right?? The component of magnetic field perpendicular to...

Hi. I'm reading a paper "Transmission of light through a single rectangular hole in a real metal" and the author refers to the incident light shown below as "p-polarized" without further specification. Note that ax > ay. Is there any convention in regarding a certain polarization as...

Homework Statement An electromagnetic wave is incident on a surface which absorbs all the electric field. Use Maxwell’s equations to determine the magnetic field on the other side of the surface. Homework Equations The Attempt at a Solution My initial thought was that ##B=0## as a varying B...

Homework Statement Note : There are no minus signs in first two options . Homework EquationsThe Attempt at a Solution The wave is propagating in +z direction whereas the electric field is varying in x direction . On reflection , there is a phase change of π . Also wave starts traveling in...

Homework Statement An E field with f = 2.45*10^9 Hz passes through a material with the following properties e_r = 10 u_r = 1 sigma = 1 (S/m) The Incident E field has peak magnitude of 300 V/m at the air to surface boundary. (a) *solved* Find the incident power density at the material...

I wonder if it is possible to generate a propagating EM wave by making a single charge oscillate in vacuum ? In practice, when we create EM waves, we (always ?) have opposite charges oscillating, like with a dipole antenna : In the dipole antenna case, I can see how the fields detach...

Hi, In Classical electromagnetic wave.. does it have definite polarization when the EM wave leaves the sun for example? Or is it in superposition and the polarization only exist after measurement just like in QM? I don't understand the Maxwell Equation. Does Superposition in Maxwell Equation...

Homework Statement Consider a wave vector which hits a plain boundary between water and air. The wave vector hits the boundary with an angle α1 measured from the vertical axis. The magnetic field amplitude has a y-component only. Also, notice: The z-axis is the horizontal axis, the x-axis is...

I know that if the intensity of a light beam with of a certain frequency varies it means the number of photons the light beam is composed of varies and not the individual photons energy. That would mean the E and B field amplitudes vary. This would mean that that the amplitudes of the E and B...

Could somebody explain me why it would not be sufficient for a radio receiver of an AM signal to simply consist in two elements: A very long antenna. A speaker/headphones. The set up would be as follows, the antenna is connected to the speaker and the other part of the speaker is grounded. My...

For using Galilean transformation, I have to assume that speed of light w.r.t. ether frame is c. W.r.t. ether frame, E = E0 eik(x-ct) W.r.t. S' frame which is moving with speed v along the direction of propagation of light, E' = E0 eik(x'-c't') Under Galilean transformation, x' = x-vt, t' = t...

I would like to know why electric field of EM waves changes it's direction to opposite when hitting a conductor surface. I know that electric field inside a conductor is zero but I am not able to connect these two situations.

Hi all, I've been able to find the answers to most of my questions in these forums, but this time I was not able to. So here goes my first post: I've been learning about thin film interference, and it all makes sense to me except for the correlation between destructive interference caused by...

What are the factors that determine the property of wave penetration of bodies? For instance we can listen to fm radio from inside the walls of a room. But visible light is unable to penetrate the walls. Similarly some metals reflect some frequency but absorb some. How atomic orbitals play...

Hi I have a question about current start signals in a simple circuit such as explained in http://amasci.com/elect/poynt/poynt.html. Turning on a switch somewhere in the circuit, sphere of influences, i.e. motions of electrons in wire and generation of Poynting vector around the wire, start from...

Hi. I'm a bit puzzled that the classical formula for the intensity of a monochromatic, linear EM wave $$I=\frac{1}{2}\cdot c\cdot \varepsilon_0\cdot E_0 ^2$$ seems to be independent of frequency whereas I find for the energy of a mechanical wave (e.g. on a string with total mass ##M##)...

Hey, guys. There is an interesting question about EM waves. I know electricity is transferred on transmission line as electromagnetic wave. But electromagnetic wave is one type of transverse wave, then how is AC electricity like? I feel it hard to imagine it. Besides, conductors could be used...

When solving the differential equations for an electromagnetic wave you get out that the electric and magnetic field oscillate in phase. But when considering a oscillating dipole, the electric and magnetic field at a point close to the dipole are a quater period out of phase. Can someone please...

There is also a classical model of a photon available, which to me explains a particular behavior of it. Can this model be proved to wrong ?

I've been trying to understand what an electromagnetic wave is, and have spent quite a while now reading around and piecing different bits of information together to try and get an answer. I haven't yet found an answer to my title question. It might just be because I have a lack of...