Electromagnetic wave Definition and 196 Threads

If the intensity of an electromagnetic wave is 80 MW/m^2, what is the amplitude of the magnetic field of this wave? (c = 3.0 x 10^8 m/s, permeability of free space ''miu subzero''= 4π × 10^-7 T ∙ m/A, permittivity of free space ''E subzero'' = 8.85 × 10^-12 C^2/N ∙ m^2) 80MW/m^2= 80,000,000...

Hi fellow members! I have a serious confusion for light being an electromagnetic wave? since the we know that electromagnetic wave is produced due to the motion of charged particle.Light reaches us from the sun due to nuclear fusion reaction but light is produced due to the heat or energy...

I understand the relationship between velocity and wavelength when the refractive index changes but I can't fully understand why frequency cannot change. What would happen if it did? why can't the speed of light stay constant as frequency and wavelength change to keep it. Is it because of...

Is there any mathematical relation between the value of charge(ie proton/electron) and radiation which is being emitted? I m sure energy is conserved in this process so does that mean electron decelerates in process of radiation ?

Hi i was wondering what's is the difference between electromagnetic waves and fields or is a field just a number of electromagnetic waves. also i was wondering is it possbile to have an electromagnetic wave where there is only a magnetic field and no electric field and vice versa Thanks

Can anybody tell me the basics of EM waves...like what constitutes EM wave...what is displaced...what are electric and magnetic field components...?

Hi What was the evidence that led Maxwell to conclude that light is an electromagnetic wave? How do we measure the strength of the electric and magentic fields of a light beam ? TIA

Would it just be the energy of the wave (i.e. E = hf)?

In the picture below http://www.geo.mtu.edu/rs/back/spectrum/e_mag.gif a bulb is placed on a wire parallel to the direction of the electric field. The bulb is directly on the x-axis where the two waves cross each other. 1. Would the bulb glow when the wire is parallel to the direction...

Hi, I am looking for clamping circuit for electromagnetic waves. I have a wave which has amplitude of 5 and -10. is it possible to clamp it to 1 and 0 respectively. I want a positive side clamp to be +1 units and negative side clamp to be 0 units. is it possible to realize using any...

My first posting after joining today so starting off "light" - I know a terrible pun but please be kind as I will ask a lot of basic and seemingly dumb questions from my simple mind in my quest to learn a lot as quickly as I can! I will try to word this as best I can but, how exactly do EM...

I am having a problem understanding a thing in a electrodynamics problem. Imagine we have a wall at x=0 made of a perfect conducting material. Imagine now we have an electromagnetic wave traveling perpendicular to the wall with the electric field polarized in the y direction and the magnetic...

[Solved] Find electric and magnetic field amplitudes in an electromagnetic wave Homework Statement Find the electric and magnetic field amplitudes in an electromagnetic wave that has an average energy density of 1 J/m^3 Homework Equations u = Energy density u = (1/2)(e0)(E^2) +...

Hello, why an electromagnetic signal propagate as wave? Wouldn't be more normal that electron travel in a beeline? Thank you.

From EM, the energy of electromagnetic wave in unit volume is \varepsilon_0 E^2. Does that mean the number of photon is \varepsilon_0 E^2/\hbar\omega ( \omega is frequency of wave)? In 1-D, E=E_0cos(\omega t+kx), then the number of photon in average is \frac{1}{(2\pi/\omega)}\int_{0}^{2\pi...

Suppose a spaceship is at 1 light year distance by Earth and it sends a message back home through an electromagnetic wave, we choose a frequency so that the wave will be a radio wave which requires little energy to produce. How do i know if the wave will reach the Earth? and what characteristics...

Hi Guys, I have a doubt. When we think of a modulated wave, consider frequency modulation for example, does the wave contain photos of gradually changing energy (or frequency)?

Homework Statement Electric and magnetic fields in many materials can be analyzed using the same relationships as for fields in vacuum, only substituting relative values of the permittivity and the permeability, ε = κε0 and μ = κmμ0, for their vacuum values, where κ is the dielectric...

Homework Statement Hi, here is the problem I'm having trouble with: The rms value of the magnitude of the magnetic field in an electromagnetic wave is Brms = 0.137 T. The intensity of this wave is approximately... Homework Equations E = cB I = (ErmsBrms) / \mu0 The Attempt at a...

Homework Statement An electromagnetic wave from a wire antenna travels (from the reader) toward the plane of the paper. At time t = 0.0 s it strikes the paper at normal incidence. At point O and t = 0.0 s, the magnetic field vector has its maximum value, 5.01E-8 T, pointing in the negative...

My teacher told us energy at a point of a progressive wave is proportional to square of amplitude, it is true for both mechanical and electromagnetic wave. But in the other lesson, he also tols us the energy of the EM wave is equal to hv, where h = Planck constant, v = frequency of the wave...

All electromagnetic waves carry energy. We kno that most of the electromagnetic radiation escapes the boundary of the "physical(corporeal) Universe". Therefore, much of the energy is radiating out to the voids spreading beyond material universe. Thus, a great amount of energy is lost...

Homework Statement Instead of sending power by a 850 kV, 1100 A transmission line, one desires to beam this energy via an electromagnetic wave. The beam has uniform intensity within a cross-sectional area of 80 m2. The speed of light is 3×10^8 m/s and the permeability of free space is 4×10^-7...

Show that the "plane wave" is a general solution to the electromagnetic wave eqatuion Homework Statement Show that the "plane wave" E=Eocos(k.r-\omegat) is a general solution of the electromagnetic wave equation. (you must derive this first)Homework Equations we were given Maxwell equations...

Hi, i read the more wavelenght has an electromagnetic wave the minus frequency it has, but how is possible to prove that? what experimenst were done? Thanks!

Homework Statement An electromagnetic wave, which has the frequency of f = 5MHz, goes from an unpermeable location, which has a permittivity of e = 2, to vacuum. Calculate the change in length of the wave. NOTE: I haven't found greek letters in the post menu, so if they're somewhere in there...

Which component E or B of an electromagnetic wave is responsible for visible effect?

Wouldn't an electromagnetic wave just be a wave of electrical energy like in water or in air?

A plane electromagnetic wave[traveling in the x-direction in an inertial frame]in vacuum is usually represented by an equation of the form: {E}{=}{E_{0}}{exp{[}{i}{(}{k}{x}{-}{\omega}{t}{)}{]}} The wave velocity[phase velocity] is given by: {c}{=}{\frac{\omega}{k}} We can perform Lorentz...

Homework Statement What is the maximum value of the electric field E at 1.0 m from a 100 W light bulb radiating in all directions? Homework Equations I feel like I should use this equation: I=(1/2)(8.85x10^-12)(c)E^2 The Attempt at a Solution When I used that equation, I didn't get...

I was looking into propagation of EM waves, and it appears there is an overlooked nuance here. It is often said that EM-waves are self-propagating because a change in the E-field causes a magnetic field nearby, so a constantly changing E-field [i.e. a "vibrating" field] causes a constantly...

Hi there! I was wondering: is it possible to break a glass using an electromagnetic wave at its resonant frequency?

Electromagnetic wave peaks don't "travel" through space? I'm just checking my understanding. When a wave travels through water, you can see the peak of the wave move gradually through space. But, it seems that an electromagnetic wave is different in that the peaks of the waves do NOT...

in E = E_0exp i(k dot r - wt) or E = cos(k dot r - wt) what does k dot r physically represent? Can r be any position in space or must it lie on the wave? (I physically understand what a dot product is)

Hi Folks, I understand that a changing magnetic field induces an electric field and a changing electric field induces a magnetic field. I also understand that the greater the time rate of change of one, the greater is the other. Now in free space, the electric and magnetic field of a wave...

Homework Statement At a particular point, the electric field associated with an electromagnetic wave is oriented in the +y direction, and the magnetic field in the +x direction. In which direction is the wave travelling? Also, what if they ask: At a particular point, the electric...

Hi, I am looking at electron beam going through a plasma. I am modelling it using two regions, the electron beam and external to the electron beam. I am using the potential formulation of electrodynamics and I am modelling a rigid electron beam and assuming cylindrical symmetry for...

Hey guys i have a question about EM waves. I know with sound waves that if you emit a inverted wave of the same amplitude it cancels the effect. Now i know that sound waves are air pressure but does the same principle work for EM waves? If so what effects would be experienced?

Explain why a plane electromagnetic wave cannot propagate through a metallic waveguide. I've tried to come up with an answer, but I haven't been able to. I thought metallic waveguides were good since they reflected the propagating wave very well, allowing the wave to move without much loss...

Homework Statement I need to determine B(rms) in terms of E(max) given a standard E-M wave. Homework Equations E = cB The Attempt at a Solution I assumed that B(max) is sqrt(2) x B(rms) and then just plugged in for B(max) in the equation above. Am I right in assuming the rms...

[I have rephrased my questions below in reply #7. Basically, could there be 2 types of Electromagnetic Energy?] Here is what I meant: Here's the thing. I understand the 'textbook' explanations for these questions already so I'm not really searching for a recital of that information. I...

Suppose a strong electromagnet is attracting a metal object and accelerating it towards the magnet. Suddenly, the power to the magnet is shut off. I presume that the object continues to accelerate for a very very brief period before moving at constant speed, because the electromagnetic wave can...

Homework Statement This question is question 5 from chapter 4 of Hecht's Optics, 4th edition. I found a pdf of the homework set, and the question is labeled as 4.5. http://www.physics.byu.edu/faculty/hess/471W09/Homework/Ch4.pdf" Homework Equations Not completely sure The...

From reviewing previous posts on the subject, I understand that the E field and B field propagate in-phase through space. From this information, does it mean that at a specific space and time the E and B fields will be zero? If we had an instrument to determine the E and B field at specific...

I've been looking all over the web for this stuff and I simply can't find anything that gives a proper explanation. What determines the speed of say, radio waves, in a medium? I know electromagnetic waves travel at the speed of light and as such I guess I can use the refractive index to...

Anybody have any experience with this book? It seems to be the standard in several graduate E&M courses in the EE dept. at MIT; custom published by them too. Is it just bound lecture notes or does it serve as a stand alone textbook? How does it compare to the "standards" such as Jackson and Balanis?

I'm not understanding something here. Maxwell's wave equation is: Laplacian of E = (1/c^2) * second partial of E (sorry, I don't know how to write symbols) But the second partial derivative is the Laplacian. So how can you scale the laplacian of E by a number and get the laplacian of E as...

Hi, I am just curious; do EM waves attenuate in a vacuum? If yes, how does this happen? Also, how do they faint through a medium?

Hi, I am trying to calculate the power of a reflected electromagnetic field and can't find a physical explanation for a given solution. I've noticed the following example: The Plane has a radar for altitude measurement which emmits the power Ptx at the frequency ftx. Calculate the power...

...would the world be a very different place? Quantum theory originally had to deal with huge problems in classical physics, above all the stability of atoms. The particle theory of light evolved in the context of experiments like the photo-electric effect and the Compton effect. In...