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PlezI want your help

  • Thread starter pop
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  • #1
pop
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plez..I want your help :(

I have HW is Difficult for me

if any body can help me :(

Q1:
1)In a conducting media the wave equation:
[tex]\Delta[/tex]^2[tex]E[/tex]=[tex]\mu[/tex][tex]\sigma[/tex][tex]dE/dt[/tex]+[tex]\mu\epsilon[/tex][tex]d2E/dt2[/tex]

has solution of the type E(z, t) = E0 exp [ i (kZ –w t)], where
[tex]\kappa[/tex]^2 = [tex]\mu\epsilon[/tex] w2 + i [tex]\mu\sigma[/tex] w.
a) Find explicit expressions for real and imaginary parts of [tex]\kappa[/tex] .
b)Show that in a good conductor the electric field leads the magnetic field by 45(deg) and find the ratio of their amplitudes. ?


Q2:
A monochromatic plane polarized electromagnetic wave
E(r, t) = E0 sin (k. r – w t) is traveling eastward.
The wave is polarized with E directed vertically up and down alternately. Calculate E, B and the Poynting vector S provided that the amplitude of the electric field strength is 0.05 V/m and the frequency = 6 MHz. Also, find the <S>?

plez I wanna the answer. befor friday night

thanx for all
 

Answers and Replies

  • #2
gabbagabbahey
Homework Helper
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Hi pop, Welcome to PF!:smile:

As per the forum rules, you need to show some attempt at a solution in order to get assistance here.
 
  • #3
tiny-tim
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Welcome to PF!

Hi pop! Welcome to PF! :smile:

(try using the X2 tag just above the Reply box :wink:)

(also, if you use LaTeX, just put tex and \tex at the start and end of each line; and ∇ is \nabla not \Delta :wink:)

Q1:
1)In a conducting media the wave equation:
2E = µ σ dE/dt + µ ε d2E/dt2

has solution of the type E(z, t) = E0 ei (kZ –w t), where
k2 = [tex]\mu\epsilon[/tex] w2 + i [tex]\mu\sigma[/tex] w.
a) Find explicit expressions for real and imaginary parts of [tex]\kappa[/tex] .
b)Show that in a good conductor the electric field leads the magnetic field by 45(deg) and find the ratio of their amplitudes. ?

For 1a), just differentiate … what equations do you get? :smile:

And that should help you with 1b) :wink:
 
  • #4
pop
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gabbagabbahey:

thanx
i read it :wink:
____________

tiny-tim

hi
For 1a), just differentiate … what equations do you get? :smile:
yah I know ....if i do this i will get :
k2 = [tex]\mu\epsilon[/tex] w2 + i [tex]\mu\sigma[/tex] w.

but i don't need this i need Eq 9.126 in Ch 9
in Griffiths. Electrodynamics 3ed :biggrin:
>> sorry i can't write it :)

any way thanx alot .....i did it

_____________

I still wait to your help in Q2

Q2:
A monochromatic plane polarized electromagnetic wave
E(r, t) = E0 sin (k. r – w t) is traveling eastward.
The wave is polarized with E directed vertically up and down alternately. Calculate E, B and the Poynting vector S provided that the amplitude of the electric field strength is 0.05 V/m and the frequency = 6 MHz. Also, find the <S>?

plez I wanna the answer. befor friday night

thanx for all
:)
 
  • #5
gabbagabbahey
Homework Helper
Gold Member
5,002
6


I still wait to your help in Q2
This forum supports LaTeX, which should make writing vector equations easier for you. For example, a general monochramitic plane wave is given by

[tex]\vec{E}(\vec{r},t)=\vec{E_0}e^{i(\vec{k}\cdot\vec{r}-\omega t)}[/tex]

....Now, as for your question, I'd start by picking a coordinate system (for example, positive x-direction="East" and "vertical"=positive y-direction) and then write explicitly the polarization unit vector and wave vector and use that to re-write [itex]\vec{E}(\vec{r},t)[/itex].

Then, use Faraday's Law to calculate [itex]\vec{B}(\vec{r},t)[/itex]. And finally calculate <S>.
 
Last edited:

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