Electromagnetic waves Definition and 322 Threads

We took electromagnetic waves this week, and They specified that only accelerated charges make electromagnetic waves. So from my previous reading on the internet about speed of causality, I came up with this. That if a charge is moving at a constant velocity, It's field follow is it...

While studying the difference between sound and light, I am puzzled by the following statement in this blog: Is this just another way of saying it doesn't need any medium? The Transmission medium Wikipedia page makes me think the vacuum of space is its "medium".

I know that light are affected by gravity since they have both momentum and energy, but what about other magnetic waves such as radio waves or x-rays or other electromagnetic waves

I know that the electromagnetic waves are alternating electric and magnetic fields. But I don't get why the fields can't stand still and alternate at the same point. Why they always move ?? I would prefer a logical and verbal answer rather than a mathematical answer. But if mathematics helps...

- What exactly is the equilibrium of the waves that is shown on graphs? My understanding is that the oscillations are in the strengths of the field, and different sides of the equilibrium represent different directions of the fields. However, I feel as though this contradicts itself in some...

(Sorry for my poor english.) I'm just wondering why is it necessary to have oscillating EM fields for life existing on Earth. The sun has a magnetic field (I think a static one), so why it's not enough to life exists? Also, why we and other animals only see the objects if the fields are oscillating?

Homework Statement Homework Equations <S>=c \epsilon E2/2 \Delta P = A \Delta t <S>/c The Attempt at a Solution My question is if we need the "box height"? This is my work which I'm assuming is wrong. :CIf there's another problem like this on here please put a link. I didn't see any, but...

(I'm sorry for my poor English.) I draw a sketch showing the intensity of the magnetic field at two points p1 and p2, where the distance from the source (a wire carrying a current, for example) to p2 is greater than it's for p1. Is the shape of the curve correct? Is it correct that t2-t1/c is...

It is well known that a circular loop of steady current does not radiate, even though each individual charge is undergoing centripetal acceleration. How about a loop of steady current that is shaped in a square? Does this structure radiate?

(sorry for my poor english) I've read that a electromagnetic wave only exists in a particular point of space if in such a point there is a nonlinear change of the electric field in respect to time. Then I took a graph calculator and I derived Coulombs equation for the electric field. The results...

1. The problem statemeent, all variables and given/known data The field electric's electromagnetic wave issued by a strut isotropic source is: \vec{E} = E_{0} r_{0}*cos(ωt − kr) \vec{θ} Find the magnetic field in spherical coordinates Homework Equations I think, i use the equation \vec{B} =...

Hi people, I studying electromagnetic waves (intermediate) and I don't understand how the expression for linear momentum of a wave is obtained, if the wave doesn't carry any mass. In particular, I have to explain why the radiation pressure on a perfect absorber is half that on a perfect...

Why are electromagentic waves not visible itself but visible if they are reflected by an object ? Assuming a source of light emitting photons. This waves are not visible in the dark. If they end up on a surface of any object which "reflects" the light we start to see the object. What happens at...

Homework Statement In a region of empty space, the magnetic field is described by ##\vec{B} = B_0e^{ax}\sin{(ky-\omega t)} \hat{z}##. Find the speed of propagation ##\vec{v}## of this field. Homework Equations ##\Delta \vec{B} = \frac{1}{v^2}\frac{d^2\vec{B}}{dt^2}## , ##k=\frac{\omega }{...

We know that EMW are generated by accelerating charges. If I accelerate a charge it should gain kinetic energy equal to half the mass of the charge times velocity squared. But at the same time it will radiate electromagnetic waves which carry energy itself. So where does this energy come from...

Is it correct to say a varying electric field creates a magnetic field and vice-versa instead of saying that a charge creates such fields?

Say you have a transmitting whip antenna. If you send a quick DC burst into it, you will get the electrons in the antenna accelerating in one direction like this: If that EM wave is then absorbed by a receiving whip antenna, the electrons will also move in one direction. The polarity of the EM...

Homework Statement Within a certain material, an EM wave with = 1 mm is attenuated to 10% of its original intensity after propagating 10 cm. Determine the imaginary part of the index of refraction ni Homework Equations 3. The Attempt at a Solution [/B] so...

I was thinking about a laser, a very strong laser, how does it "burn" things? And what about the microwave oven? What happens in the atomic scale? I know that when something has an increase in temperature the atoms moves quicky because the the temperature is proportional to the kinetic energy...

I have two questions which has been troubling me: 1. How can we say that meaning of e^(jkR) is a spherical wave traveling in negative R direction. It can be viewed as polar form of vector with magnitude 1, but how a spherical wave? 2. When we take instantaneous value of a complex quantity , why...

Is this phenomenon explicable with the simple laws of electromagnetism alone?

Homework Statement Calculate electric field and magnetic field produced by radiation emitted by a 100 W bulb at a distance of 1 m if radiation efficiency is only 5%. Homework EquationsThe Attempt at a Solution I only know how to find intensity due to the bulb: I = P/4πr2 = 5/4π W/m2 I have...

Ive been wondering about this for about two days and i have a simple question and that is , if I have two photons that are 180 degrees out of phase, passing through a surface perpendicular to the photons velocity vector then will the EM fields exert tension on the surface?(in this case the...

Hello, I am trying to find the magnetic field that accompanies a time dependent periodic electric field from Faraday's law. The question states that we should 'set to zero' a time dependent component of the magnetic field which is not determined by Faraday's law. I don't understand what is...

Homework Statement We look at the center of one face of a solid cube of glass on a line of sight making 55° with the normal to the cube face. What is the minimum refractive index of glass for which you will see through the opposite face of the cube? (Hint: see through will be possible if the...

" Thus according to Maxwell, light waves are associated with changing electric and magnetic fields; changing electric field produces a time and space varying magnetic field and a changing magnetic field produces a time and space varying electric field. The changing electric and magnetic fields...

The book is expensive, so I want a book like Bekefi's and Barrett's Electromagnetic Vibrations,Waves,Radiation. Preferably at a higher level than this book. Thank you!

there are no electromagnetic waves? All I know is that there is a modified version of the Maxwell equations (in differential form) for such a universe, such as (the arrows represent vector arrows): →∇x →B = μ0 →j + μ0 ε0 ∂→B/∂t instead of having ∂E/dt in the last term (which would be the case...

Hi https://en.wikipedia.org/wiki/Mathematical_descriptions_of_opacity it is mentioned above that "in non attenuating media, the refractive index and angular wavenumber are related by: A complex refractive index can therefore be defined in terms of the complex angular wavenumber defined...

For electromagnetic wave if it's reflected from a perfect conductor standing wave can be form. I wonder why Poynting vector can be used to describe the intensity of standing EM wave. (see p.19 of http://web.mit.edu/viz/EM/visualizations/coursenotes/modules/guide13.pdf ). From some textbooks...

Can someone correct my understanding on electromagnetic waves please; I've clearly got the wrong end of a stick somewhere, but can't figure out where my misunderstanding is! Thanks. If I draw a classic EM wave with the electric field on the up and down axis and the magnetic field at right...

I'm trying to derive the law of reflection for Electromagnetic Waves and Optics. I'm using some lecture notes that my university provided. I'm confused as to why the two sine functions are changed to cosine functions as you don't do the same when you are deriving Snell's law. Refer to attached...

In the attached figure, light is incident at angle $${\theta}_{1} = 40.1^{\circ}$$ on a boundary between two transparent materials. Some of the light travels down through the next three layers of transparent materials, while some of it reflects upward and then escapes into the air. If $${n}_{1}...

Dear all, I’d like to ask your help concerning some doubts about electromagnetic waves, Faraday’s cage, and so on. I read recently that an instrument with a transmitter that emits a low frequency electromagnetic field (around 15 to 22 Hz) located inside a metal pipeline could communicate with...

I have coils to transmit and receive the power supplied.When we supply the transmitter , it omit the electromagnetic wave.Does it omit one electromagnetic wave or a lot of them? If there are several of them, is the energy supplied ,divided equally to the number of waves or every wave carries the...

Is there a theoretical way to force electromagnetic waves transfere energy point to point like electricity instead omni-dirrectionally? I think it might be helpful for looseles wireless energy transfere.

Hello. Sorry if my question sounds somewhat weird (I'm a mathematician, not a physicist). I am trying to understand something for my work. I would like to know what is your opinion about it. Assume that there are two electrodes inside a vacuum tube, with a difference of potential between them...

Are the angular frequency in electromagnetic waves and frequency of a photon characterise the same physical quantity? I know that these come under two different theory, but I want to know whether these names (angular frequency of em wave and frequency of photon) mean the same physical quantity...

how can the electromagnetic waves be transverse and at the same time the E.M propagates in space (the definition of the transverse wave is that it is a wave in which it's medium particles propagate perpendicular to the direction of wave propagation) what i don't understand is that how can it...

I am an 8th grade science teacher who has regularly used the pre-Bohr planetary-like model of the atom (like most 8th grade science teachers and textbooks) to help students start to understand atomic physics. But in my free time, I have repeatedly tried, and failed, to really understand the...

Quick question about electromagnetic waves traveling through what's basically a capacitor. In the picture I have labelled areas that I'm curious about. 1. Is there a potential induced at A? 2. If yes, is it localized? I suspect the potential would be different at A and B. 3. Is it correct to...

Homework Statement A plane harmonic electromagnetic wave of amplitude Eo and frequency wo is traveling in the positive x direction in a vacuum. It is linearly polarized with its plane of vibration at 45 degrees to the xy plane and the electric field is zero when x=0 and t=0 a) Make a sketch...

I've seen derivations for c=E/B and c=1/√μ0ε0, but I don't seem to get the directions right. i.e. I end up with a negative sign in one of the equations. The derivations I've seen do not use vector calculus. One derivation I've seen is in http://Derivation[/PLAIN] of Electromagnetic Waves from...

When I observe the UV light emitted, I can literally see the millions of photons appear and die within milliseconds, but nobody else around me can. When I observe IF light sources and transmitters in low light, it is the same characteristic, except there only appears to be to photon sources, and...

Hi! I have a question regarding the radiation coming from the sun. It might seem stupid to some people but I would really like to know how this works. When you see images of the sun's rays reaching the Earth for example on this image from wikipedia (see attached image). The rays are almost...

Homework Statement In the spectrum of the blue part in a candle flame, there’s a violet emission at 432 nm due to excited CH* molecules (chemiluminescence). Why 432? Why not 400 or 500? There are emissions at 436, 475 and 520 nm too. Why these numbers? 2. The attempt at a solution Is it...

Can anyone give a solution or guidance about how to solve this. In vacuum, the components of an EM wave are Ey = 50(V/m)cos[(5.00 m-1)x + ωt], Ex = 0, and Ez = 0. What is ω?

I'm a little confused regarding the maths of TE and TM modes. Solving the following system for TE (which derives from Ey(x, z, t) = Em(x) = exp[i(ωt-βz)] ): Asin(px) + Bcos(px) , -d/2 < x <d/2 Cexp(-qx), x>d/2 Dexp(qx), x<-d/2 we conclude in two types of solutions for TE modes: symmetric...

Homework Statement Hey, I've been given this EM-wave: (-2\vec{e}_x+2\sqrt{3}\vec{e}_y+3\vec{e}_z)E_0e^{i[\omega t-a(\sqrt{3}x+y)]} with a∈ℝ 1) Describe the wave and how it's polarized. 2) In what direction does the wave propagate? 3) What is the phase velocity of the wave? 4) What is the...

1. The power radiated by the sun is 3.9 x 10^26 W. The Earth orbits the sun in a nearly circular orbit of radius 1.5 x 10^11 m. The Earth's axis of rotation is tilted by 27 degrees relative to the plane of orbit, so sunlight does not strike the equator perpendicularly. What power strikes a...