Electromagnetic waves Definition and 328 Threads

We have the following constitutive relations: $$ \vec D= \epsilon_0 \vec E +\vec P$$ $$\vec B=\mu_0\vec H + \vec M$$ And Maxwell's equations are: $$\nabla\cdot\vec D = \rho$$ $$\nabla\cdot \vec B=0$$ $$\nabla\times\vec E=-\frac{\partial\vec B}{\partial t}$$ $$\nabla\times\vec H=\vec j...

We know a way of measuring energy of a electromagnetic wave is the Poynting vector, which is independent of the frequency. But let's say we want to make two different electromagnetic waves, with different wavelengths and so different frequency, but with the same amplitude (so same Poynting...

Is the doppler effect on electromagnetic waves receive by cell phone in fast car and so somebody talk with cell phone in fast car view this effect

Hello ! I have a doubt as to how is this case, if it occurs, of the constructive interference of two harmonic electromagnetic waves but of different wavelengths or frequencies between them. That is, if between the two electromagnetic waves a new and unique electromagnetic wave is created and...

Hello ! As we know by definition that: "Constructive interference occurs when the phase difference between the waves is an even multiple of π (180°), whereas destructive interference occurs when the difference is an odd multiple of π." But my question is in the case of destructive...

in a nutshell what are the differences between gravitational and electromagnetic waves?

Hello I'm new to this forum and interested in astrophysics and metaphysics. My first question here is if we can create nano sized wormholes to send information faster than light to other stars for example. We don't need to travel if we could send small satellites or even just radiowaves to the...

Hi, I saw that the group velocity for an electromagnetic wave can be calculate with the following formula ##v_g = v_p + k \frac{d v_p}{dk}## Thus, since ##v_p = \frac{c}{n} = \frac{\omega}{k}## Is it correct to say that ##v_g = \frac{c}{n} + k(- \frac{\omega}{k^2})## where ##k =...

I read in a book that high frequency electromagnetic waves are more able to penetrate than low ones , so why radio waves can penetrate walls when light cannot?

Hi! So I'm trying to understand electromagnetic waves but I encountered different definitions: one in terms of electrons and one in terms of photons. Which ones are actually used to produce electromagnetic waves and how? Also, I saw that alternating current generates electro magnetic waves, but...

Hi ! It catches my attention that atomic particles such as protons, neutornes, electrons and their respective subparticles such as Quarks are theoretically formed by high-energy electromagnetic fields such as gamma rays and then the gravitational field that would generate the mass of these...

My Try: The resultant field is given by $$\begin{aligned}\overrightarrow{E}=\overrightarrow{E}_{1}+\overrightarrow{E}_{2}=\widehat{i} E_{0}\cos \omega t+\widehat{j}E_{0}\cos \left( \omega t+\phi \right) \\ \Rightarrow E^{2}=E_{0}^{2}\cos ^{2}\omega t+E_{0}^{2}\cos ^{2}\left( \omega t+\phi...

Hi all! These days I am brushing up my knowledge on EM Waves. I begin with the introductory level but I don't mind to engage in an advanced treatment of the topic. At the very basic level I had a high school book, the mentions straightway that if the wave carries with it an energy U, it posses...

By rearranging over and over ratio formulas involving frequency, speed and wavelength, I came up with the equation: fP/fQ=10^-8xVP/VQ This led me to take into account only rows A, B, E, and F... but I can't really understand which one of these is the right one.

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Imagine that we have an electromagnetic wave or light propagating in x direction, and \mathbf{E} is oscillating in z direction and \mathbf{B} in y direction. The picture looks something like this Now, if there exists a charged particle q on the xx axis at rest, then our B field can't do...

I'm wondering if plants are sensitive to electromagnetic (EM) waves? Of course I'm not speaking of light but in the low frequency domain, say from 0 Hz to 100 kHz? I looked up the web but couldn't find anything, only experiments with EM waves above the range of 300 Mhz. Has there been any...

We're trying to prove this: There exists 3 distinct regions: Region 1 has index of refraction 1 and lies before light hits the coating. For simplicity, define the position of the interface between the air and the coating z=0. The second region is the coating, which has index of refraction √n. At...

Homework Statement: A radio station on the surface of the Earth radiates a sinusoidal wave with an average total power of 50 kw. Assuming that the transmitter radiates equally in all the directions above the ground, at a distance of 100 km from the antenna (ε0 = 8.85 10-12 C2N-1m-2) Homework...

When an object is hot its particles are moving faster than when is cold, right? I've searched that particles are electrons and protons, so it means that if we warm a object the electrons will be moving or even accelerating. Every charge accelerated creates Electromagnetic Waves (or light)...

Electromagnetic waves are oscillations of the electrical/magnetic field which propogate through space. So one might predict that the presence of a magnet/charged particle would effect their propogation somehow, like distortion or interference (eg, light might get refracted in a magnetic field or...

Light is said to consist of photons or electromagnetic waves. I'm not asking which view is correct, what conditions make one view or the other more useful, or advantages and disadvantages of each view. I am assuming the two views are compatible to the extent that the wave character of light can...

do electricmagnetic wave moving in upside down form? So the highest position is wave crest and the lowest is wave trough?

Basically as the title says. I'm interested in the naturally occurring EM waves, and I would like to know the strongest EM waves out there. I'm not talking about "strong" as in energy per photon that is proportional to the frequency, but about the overall energy transported by the wave that is...

If a source emits high frequency electromagnetic wave, for example gamma rays, does it imply that it also emits all the waves of lesser frequency?

Hi! I'm trying to solve a problem and I'm lost. Would someone kindly help me with the solution, please? 1. Homework Statement A plain electromagnetic wave with a 20GHz frequency moves in the positive direction of the Y axis and its magnetic field is oriented along the Z axis. The amplitude of...

Hello all again, I was just thinking again about another aspect of electromagnetic waves: Assume we have a planar wave. How "broad" is it or how far does the electric field of it reach? For instance if we have a single planar wave, assume the k-vector in the direction of propagation and then the...

Hello all, after thinking about properties of electromagnetic waves, especially concerning the electric field of them, I ran into some serious understanding problems: 1) photons are electromagnetic waves and vice versa and they convey electrical force. Let's now do a thought experiment: let's...

Per the maxwell equations, we know that em waves travel at the velocity of light, but that is not a sufficient condition to say that electromagnetic waves are light. How do we know that electromagnetic waves are light? They could just be something that has the same velocity as light. Any...

Hello, I've been reading up on this topic and have a couple of questions. This videos shows what I am referring to: 1. What makes the electromagnetic waves from a dipol antenna spread out? There would have to be some type of force that pushed them outwards, right? 2. When the electromagnetic...

There are some things that confuse me about electromagnetic waves, and I haven't found good answers anywhere. Consider the following equation: E=E0 e i(wt-kx) (here E and E0 are vectors, I couldn't find the right symbols). The things that confuse me are the following: 1° We say that the power...

I have learned about the electric fields of static charges and those of moving charges. From what I gather(although I have not really learned the specifics) when charges are accelerated they emit electromagntic waves which are essentialy an electromagnetic field progagating through space. My...

Homework Statement A plane electromagnetic wave travels upward. At t = 0, x = 0, its electric field has the value E = 5 V/m and points eastward. What is the wave's magnetic field at t = 0, x = 0? Homework Equations B=B init. sin(kx-wt) E=E inti. sin(kx-wt) E=cB The Attempt at a Solution I am...

Hi to everybody ! I was thinking about something which confuses me about wave emission. The question is simply the following: Does an electron emit light when it accelerate? or just during its deceleration? or maybe when acceleration and deceleration alternates in some order? I'm not really...

Do electromagnetic waves have potential and kinetic energy like springs, strings, etc. If so how are they calculated, inter-related? What is the total energy? Are the energies fluctuating over time? I am a physics hobbyist so generally the first answers should come with the least mathematics...

Hello everybody, I am new here :) what exactly is the energy of the wave? how to think about it generally, in electromagnetic waves and in relation to amplitude? I can think about the kinetic or potential energy that a particle can get from that kind of wave or the sum of all such energy in all...

Homework Statement An EM wave from air enters a medium. The electric fields are --> ^ E1 = E01 cos(2πv(z/c-t) x --> ^ E2 =E02cos(k(2z-ct)x in a medium ,where the wave number k and frequency v refer to their value in air.the medium...

Homework Statement A cell phone sends and receives electromagnetic waves in the microwave frequency range. Explain the physics of how an oscillator creates these waves. Homework Equations n/a The Attempt at a Solution An electromagnetic wave is created by the functioning of the oscillator...

Hello, I am reading a book on the history of the universe. The book says that we can still detect the electromagnetic waves generated at the big bang in the form of white noise. I am not sure how it works, because the waves transmitted by AM or FM radio antennas die down after propagating some...

I am studying about the cavity radiation inside a metallic cube. In the textbook it states that there are two independent waves corresponding to the two possible states of polarization of electromagnetic waves. What does it mean by this? (My current assumption is the phase change of the waves)...

That is, a field that accelerates charges in opposite directions on each side of an axis. I was thinking about interference of similarly polarized waves traveling in opposite directions (so that electric field peaks and valleys overlap but magnetic field adds constructively) - would there be an...

when it is asked that why radio waves do not interact with the magnetic field of electric wires or magnets, people say that radio waves are not "matter" and they do not have "charge". i really can not understand this for ex think about 2 magnets. The magnet A has a magnetic field and when we put...

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...

In classical physics, EM waves propagate this is one of the main features of all waves in general. Usually for mechanical waves the elements (like molecules) that vibrate do some little motion. For example a string can move up and down, but the waves travel further through propagation. The...

If we move towards a source of EM waves, in our reference frame the frequency appears (and it is) higher than what a stationary observer will see due to Doppler effect. The field transformations show that these two observers will se static fields differently so I would also expect that the peak...

I know this question might be too simplified but, What is the primary causes generation of light (electromagnetic waves) by electron? Is it vibration motion of electron or the motion of electron around the nucleus?

Theoretically speaking, does the frequency of em wave range from 0 to infinity?

We have materials that have negative effective permittivity and permeability. In such materials, when the product of permittivity and permeability is negative, solving the wave equation yields a wave with a purely imaginary wave number. Does this mean complete attenuation of the wave ?

What I know: A ripple/wave in a field gives rise to a particle. For example, a ripple in electric field creates a photon. Question: Is this the same principle as probability wave which when observed reveals a particle?

So I know that EM waves travel perpendicular to the electric and magnetic fields which are also perpendicular to each other. What I'm having difficulty understanding is since light is an EM wave and can travel through the vacuum of space, does that imply that everywhere in the universe there is...