Em wave Definition and 214 Threads

  1. Y

    Characterize EM wave propagate in +z and -z

    For RHC EM wave travel in +z direction, the unit vector is \hat {E}=\frac{\hat {x}+\hat{y}j}{\sqrt{2}} ignoring the ωt-kz. What if the RHC EM wave travels in -z direction? The unit vector should be \hat {E}=\frac{\hat {x}-\hat{y}j}{\sqrt{2}} ignoring the ωt+kz. Am I correct?
  2. A

    Propagating a Gaussian-Profile EM Wave in a Medium

    Homework Statement Hi everyone, As part of my final year project I am modelling the propagation of an electromagnetic wave through a medium of refractive index, n. I begin at the boundary between vacuum and the medium, x = 0 and propagate forward to some distance x. I have initially...
  3. Y

    Please verify my derivation on elliptical polarization of EM wave

    This is not a home work, it is part of the textbook on elliptical polarization. Attached is a page in Kraus Antenna book, I cannot verify the equation on the last line. Here is my work E_y=E_2(\sin{\omega} t \cos \delta \;+\; \cos \omega {t} \sin \delta) , \sin\omega {t} =\frac {E_x}{E_1}\;,\...
  4. C

    Why do metal boxes block EM waves?

    A metal box will block most EM waves. Is this because the oscillating E field will be canceled when in contact with the conductor. And because the oscillating E field is the source of the changing B field does this then kill the B field.
  5. J

    So if FM radio signals modulate the frequency of the EM wave

    then how can you tune into, say, 101.1 when its not at 101.1 MHz all the time given the frequency change?
  6. Drakkith

    EM Wave Phase - Fewer Photons at 0 Degrees?

    Let's say we have a radio wave coming into a receiver. When the phase is near 0, does this mean that fewer photons are being absorbed by the receiver compared to when the phase is near 90? (Hope I'm using the right terms here)
  7. M

    Can EM Wave Components Be Split for Enhanced Applications?

    Hi eveyone, I am new to this forum and I hope that I can gain lots from this forum. Recently, one question comes into my mind, that is about the possibility of splitting the electric component and magnetic component of EM wave. This two components seem to always stick together. However, if...
  8. J

    Emission of EM Wave: Why Does it Happen?

    In wikipedia's description of transmitter, if an alternating current is given to an antenna, then the antenna radiates off em wave. But why this happens so?
  9. N

    Something to be clarified about EM Wave: TE, TM and TEM

    I have been reading different articles about EM wave modes, it is said that in TE waves the E_z is zero, similarly for TM H_z is zero, and TEM both E_z and H_z are zero. How about the E_x and E_y in TE wave? Someone said E_y is also zero and only E_x exists in TE...is this true? Is it...
  10. C

    How does the amplitude on a EM wave graph correspond to the number of photons?

    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...
  11. T

    Direction of propagation of an EM wave

    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...
  12. Drakkith

    Understanding Vector in EM Wave

    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...
  13. H

    Focusing EM wave and the Linear Superposition Principle

    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...
  14. E

    EM wave at a plane dielectric boundary

    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...
  15. M

    Frequency of EM wave from linearly accelerating charge.

    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...
  16. D

    Does EM Wave induce emf in coil?

    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?
  17. K

    EM wave function & photon state vector.

    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...
  18. A

    In-plane wave vector of em wave

    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?
  19. U

    Dissipation Rate of a Propagating EM Wave

    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...
  20. S

    Maxwell's Eqns- HELP - Spherical EM wave

    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...
  21. W

    Wavefunction vs EM wave of a Photon

    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...
  22. K

    Questions about EM wave in material

    How can I find the induced current density by EM wave in a material? Should I have ma = Fbinding + Fdriving + Fdamping like treating it as a spring? Then the current density should be charge density of the material x velocity (ρv), isn't it? Is there any condition the EM wave cannot...
  23. P

    A 50cm wavelength EM wave in air has 50mW/m^2 of energy.

    Homework Statement A 50cm wavelength EM wave in air has 50mW/m^2 of energy. what is the frequency? what is the average E field? What is the B field strength? What would be the λ in water? Homework Equations I found the λ. How do I find it in water The Attempt at a Solution...
  24. S

    How to Adjust Frequency of EM Wave

    Alternating current produces EM Wave. What determines the frequency(or wave length) of an EM wave related to current or voltage?
  25. A

    Momentum density vector of a plane em wave

    Homework Statement Show that in vacuum the magnitude of the momentum density vector of a plane electromagnetic wave is equal to the energy density divided by the speed of light, c. Homework Equations \vec{S} = \vec{E}x\vec{H} The Attempt at a Solution This doesn't seem too hard if you know...
  26. C

    2 Questions about EM wave propagation

    I was just reading about EM wave propagation and had two questions I would appreciate an answer to. 1-I read how the electric and magnetic fields of an EM wave oscillate sinusoidally and perpendicular to each other and the direction the wave is traveling. Is there any significance or special...
  27. L

    Which Direction Does the Electric Field Oscillate and the Wave Propagate?

    Homework Statement Given the following EM wave propagating in vacuum, find the direction along which the electric field oscillates and the direction of propagation of the wave: \vec{E} = (-3\hat{i} + 3\sqrt{3}\hat{j}) 10^4 e^{i[\frac{\pi}{3} (\sqrt{5}x + \sqrt{5/3} y10^7 - 8.1246 *10^{15} t]}...
  28. P

    Why do electromagnetic waves use complex numbers?

    why electromagnetic waves are represented by complex numbers?
  29. A

    Show EM Wave equation invariant under a Lorentz Transformation

    Homework Statement Show that the electromagnetic wave equation \frac{\partial^{2}\phi}{\partial x^{2}} + \frac{\partial^{2}\phi}{\partial y^{2}} + \frac{\partial^{2}\phi}{\partial z^{2}} - \frac{1}{c^2}\frac{\partial^{2} \phi}{\partial t^2} is invariant under a Lorentz transformation...
  30. P

    Can I Make a 5-Lambda EM Wave?

    is it possible to make am em wave of length 5(lamda)...lamda=wavelength of em wave...
  31. Y

    EM wave right above and right below the conducting surface.

    Assume a infinite depth good conductor block with width in y and length in x direction. Boundary is at z=0 and air is at z=-ve and conductor at z=+ve. Let a voltage apply across the length of the block in x direction so a current density established in +ve x direction. We want to look at the EM...
  32. Y

    Question on EM wave in space and matters.

    My understanding from the book about EM wave that E and B is perpendicular to the direction of propagation only in medium that is charge free so \nabla \cdot \vec E = 0. What cases when E and B not perpendicular to the direction of propagation? Thanks Alan
  33. P

    Light as an EM wave to explain photoelectric effect?

    OK, so recently I have learned that in the early 20th century, while Max Planck was attempting to explain the quantum nature of light, two men named Philip Lenard and Heinrich Hertz discovered the photoelectric effect. They found that an electron must absorb a specific amount of energy...
  34. Q

    Phase invariance of an EM wave in special relativity

    Homework Statement So I'm trying to show for a specific, given EM plane wave in vacuum that kx - \omega t = k' x' - \omega' t' but I'm running into some difficulties. I'm hoping someone can show me where I'm going wrong. Here's the setup: In the lab frame K, a plane EM wave traveling in...
  35. G

    Spherical EM wave or one or more photons?

    My understanding is that the EM field at r.t generated by a radiating source can be described as the amplitude of the EM fields at r, at time t. Is there a corresponding photon associated with that wave? A unit surface area at large r from the source will have less energy passing through it...
  36. Q

    Understanding EM Wave Equations

    hi, i have a problem understanding why the wave equations are as such if wave is moving left, it is f(z,t) = Acos(kz + wt - d) if wave moving right , f(z,t) = Acos(-kz -wt + d) finally i don't know what this represent f(z,t) = Acos(kz - wt + d) where A is constant , k is wave...
  37. M

    EM Wave - Where Does the Energy Go?

    For an EM wave in vacuum, we know the energy density is given by1/2 e E^2 for the electric field, with a similar expression for the magnetic (e is permittivity of vacuum). E^2 implies that the energy oscillates as a cosine squares function if we represent the E field as E_0.cos [ kx -...
  38. P

    Does waving a magnet back and fourth produce an EM wave?

    If you take a permanent magnet and wave it back and fourth, or even just move it along in one direction, this seems like it should create an electromagnetic wave. If so, how would one compute the frequency, and could you possibly detect it with a radio if you shielded it from other noise?
  39. J

    Are the E and B fields in phase in an EM wave?

    I keep looking at a sketch of the mutually perpendicular electric & magnetic fields in an EM wave. The sketch (and my text) says they are in phase, i.e. their maximum values occur simultaneously, ... ...but the discussion centers around the changing E field producing the B field and...
  40. N

    Can an Electromagnetic Wave Charge a Battery?

    This is a theoretical question not a homework question, so if this is the wrong section to post this in please let me know. But my friend has this idea that if he sent an electromagnetic wave at a certain frequency at a surface it could create a current and this in turn could charge a battery...
  41. D

    EM Wave Boundary Layer Question

    I understand application of Snell's law for transition from one medium to another but I have a question regarding this model. When an electromagnetic wave transitions from air into a conductive medium does the wavelength change instantaneously as the theory seems to imply or is there a boundary...
  42. K

    Why Do Electrons Emit EM Waves and Lose Energy in Classical Orbits?

    why according to classical, electron circuling around the nucleus will emit EM wave and lose energy and collapse? I know electron undergoes circular acceleration, but why emit EM wave?
  43. V

    Maxwell's Derivation of EM Wave Momentum: E/c

    How did maxwell derive the momentum of electromagnetic wave to be E/c ?
  44. N

    Does an EM wave bend in a B-field?

    I read somewhere that Thomson (1897) concluded that the electron was not an EM wave because it bended in a magnetic field and that it had been proven that EM waves did not do this. Is this true?
  45. B

    How to study EM wave interactions via internet?

    I would like to do some reading about how EM waves interact with each other via internet. Upon googling "EM wave interaction," I got some general links about EM radiation and some book titles but I didn't see any websites. Does anyone know one or more good online sources that give an overview...
  46. X

    Frequency & Wavelenght of EM wave

    Frequency & Wavelenght of EM wave! Hi..on some other thread i found this link showing animation of propagation EM wave: http://www.molphys.leidenuniv.nl/monos/smo/index.html?basics/light_anim.htm it has cleared my one doubt, because i used to think that EM wave is like an invisible line...
  47. H

    Narrow EM wave beam - how it propagates

    Consider a narrow beam of EM waves that propagates in the Z direction and is concentrated near the YZ plane, so its intensity fades rapidly as we move away from the YZ plane in the X direction. Let the E field be in the X direction. Consider a cube with edges parallel to the X, Y and Z axes...
  48. M

    Finding the average energy density of an EM wave in a magnetic field

    Hi, I've not posted on here before but I'm trying to keep on top of work over the summer and I'm having some real problems with this question Homework Statement Consider the plane polarised EM wave in a source free vacuum with magnetic field B = (1,1,0)B0cos(kz-wt) where B0 = 0.001T. Find...
  49. A

    Does the E Vector of a Polarized EM Wave Trace an Ellipse in Space?

    Let us consider the Electric field components of a polarized EM wave . [PLAIN]http://www.cdeep.iitb.ac.in/nptel/Electrical%20&%20Comm%20Engg/Transmission%20Lines%20and%20EM%20Waves/graphics/CHAP%204__255.png. Now if we fix the value of z (for convenience take z=0) and consider the locus of...
  50. R

    Can sound wave also interference just like EM wave

    its my exam question.. i am not so sure... but i put it can't because sound is a wave of vibration which it can diffract but not interence... but i don't know.. can sound wave interference? cheers
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