Verifying Answer to Wave Equation and Associated B Field

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Discussion Overview

The discussion revolves around verifying the derivation of the wave equation for the electric field (E) in empty space, as well as finding the associated magnetic field (B) using Maxwell's equations. The scope includes theoretical derivation and mathematical reasoning related to electromagnetic theory.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant presents a derivation of the wave equation for E, stating that the Laplacian of E equals epsilon-0.mu-0 times the second time derivative of E.
  • The same participant claims to have solved the wave equation to find E = eyEycos(wt - kx) and seeks confirmation of this result.
  • Another participant questions the calculation of the curl of E and suggests that it should be evaluated correctly to find B.
  • A further reply emphasizes that the curl of E is a vector quantity and should have multiple components, indicating a potential error in the initial calculations.

Areas of Agreement / Disagreement

Participants express disagreement regarding the correctness of the calculations related to the curl of E and the subsequent derivation of B. There is no consensus on the validity of the initial derivation or the method used to find the associated magnetic field.

Contextual Notes

Participants highlight potential issues with the integration of the curl of E and the representation of its components, suggesting that assumptions about the vector nature of E may not have been adequately addressed.

Hoofbeat
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Hi, I have the following question on my problem sheet, and I just want to check that my answer to it is correct as I need to use the result in a later problem. If someone could confirm it is correct, or point out mistakes/erros that would be great.

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Q. Derive the wave equation for E in empty space (Form the curl of Maxwell II and use a vector identity.). Find the condition that the plane wave E = eyEycos(wt - kx) is a solution (k=2pi/lamda). Use Maxwell II to find the B field associated with this electric field.
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A. I've done the derivation fine to get:

Laplacian E = epsilon-0.mu-0. d^2E/dt^2 [these are partial derivatives]

this is the same as d^2E/dx^2 = (1/c^2).(d^2E/dt^2) which can be solved using separation of variables to get E = eyEycos(wt - kx).

To find the associated B field, we used Maxwell II, ie. curlE = -dB/dt.

CurlE = -keyEysin(wt - kx)

B = integral - [curl E] dt

B = k/w. eyEycos(wt - kx)

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Thanks
 
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[tex]\vec{B}=-\int dt \nabla\times\vec{E}[/tex]

What is the curl of [itex]\vec{E}[/itex]...?And then evaluate the integral correctly.

Daniel.
 
dextercioby said:
[tex]\vec{B}=-\int dt \nabla\times\vec{E}[/tex]

What is the curl of [itex]\vec{E}[/itex]...?And then evaluate the integral correctly.

Daniel.

Isn't the curl of E in this case, just the value of E calculated earlier, integrated wrt x?
 
That curl is a vector and should have 2 components,namely on [itex]Ox_{1}[/itex] and [itex]Ox_{3}[/itex] axis of coordinates...

So it's incorrect what you have written.Please do the calculations again.

Daniel.
 

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