Read about electromagnetic waves | 49 Discussions | Page 1

  1. Adesh

    I Derivation of [itex] p = \frac{E}{c} [/itex] using Maxwell's light

    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...
  2. GuillemVS

    I Electromagnetic Waves and different energy manifestations

    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)...
  3. A

    I What are the most intense electromagnetic waves in nature?

    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...
  4. Cathr

    I Electromagnetic wave equation - phase and amplitude

    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...
  5. P

    An Electromagnetic wave goes from air into a medium...

    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...
  6. I

    I Two States of Polarization of EM Waves

    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)...
  7. C

    I Can an axisymmetric electric field be created without charges?

    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 travelling in opposite directions (so that electric field peaks and valleys overlap but magnetic field adds constructively) - would there be an...
  8. L

    How to determine the direction of the E-field of an EM wave

    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...
  9. Vaibhav Sahu

    A Propagation of EM Waves in metamaterials

    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 ?
  10. Ian Baughman

    I Understanding Electromagnetic Waves

    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...
  11. S

    B EM wave medium

    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".
  12. T

    B Are all electromagnetic waves affected by gravity?

    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
  13. DrPapper

    Momentum in a Box of Light

    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. :C If there's another problem like this on here please put a link. I didn't see any...
  14. S

    I Radiation from a Square Loop of Current

    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?
  15. D

    Spherical waves

    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} =...
  16. D

    Why E/c = p ?

    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...
  17. adremja

    EM wave with circular polarization interferes with conductor

    Homework Statement EM wave with circular polarization travels in directon z interferes with perfect conducting surface xy. 1. find reflected wave 2. calculate induced charge density and surface current induced on conducting surface Can you verify if I started point 1. correctly, and give...
  18. It's me

    Velocity of propagation of an EM field in vacuum

    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 }{...
  19. J

    Refraction index

    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...
  20. T

    Question regarding waves

    I have two questions which has been troubling me: 1. How can we say that meaning of e^(jkR) is a spherical wave travelling 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 ...
  21. M

    How can I find the minimum index of refraction?

    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...
  22. J

    Classical Book like Barret/Bekefi's Electromagnetic Vibrations?

    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!
  23. R

    How would one describe the universe in which

    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...
  24. A

    Mathematical descriptions of opacity

    Hi 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...
  25. kelvin490

    Question about intensity of EM waves

    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 ). From some textbooks...
  26. mgkii

    Energy at zero axis in an Electromagnetic field?

    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...
  27. KaseyKC

    Deriving the law of reflection

    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...
  28. M

    Faraday's cage supposed to doesn't work for low frequency

    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...
  29. C

    Wave propagating inside moving charged particles

    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...
  30. Jordaniel

    Why do I see UV & IF light? And why do I see visual "noise"?

    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...