All Questions
35
questions
2
votes
1
answer
36
views
In magnetrons, is it the accelerating electrons or alternating fields within the anode that produce the microwaves?
Doing a report for a school project and want to get to the bottom of the radiation source within a microwave oven:
According to Maxwell's equations don't the accelerating electrons (accelerating ...
- 21
1
vote
2
answers
61
views
Difference between solution for Rectangular hollow wave guide and resonant cavity
In Griffith's Introduction to Electrodynamics, he solves for $\vec{E}$ and $\vec{B}$ in a Rectangular waveguide assuming they take the "generic form"
$$\vec{E}(x,y,z,t) = \vec{E_0}(x,y) e^{i(...
- 460
0
votes
2
answers
123
views
How do all elecromagnetic waves travel at the same speed, if some have shorter wavelengths and therefore take a more circuitous route from A to B? [duplicate]
Starting point: "electromagnetic waves of all frequencies travel through space at the same fixed speed - the speed of light". Hawking (The Universe in a Nutshell).
Which of the following ...
- 11
1
vote
2
answers
367
views
A simplified derivation of $E_o=B_o C$ , without maxwell's wave equation
I recently came across the following equation in my physics course
$$E_o=B_o *c$$ ,where $E_o$ is the amplitude of the electric field, $B_o$ that of the magnetic field, and $c$ the speed of light
...
1
vote
2
answers
929
views
Why is the electromagnetic wave equation derived from Maxwell's equations with no charges?
After having consulted numerous physics books, forums and videos, in all cases I found that the electromagnetic wave equation is derived from taking as a premise that the medium is a vacuum. This ...
- 113
2
votes
2
answers
108
views
Confusion in the showing EM wave exist from Maxwell equation
When deriving the mathematical description of a field, we set the current density and charge to zero in Maxwell's equations.
However, this condition is not absolutely true anywhere on earth.
Yet, we ...
- 7,980
-2
votes
1
answer
986
views
Why is the wave impedance calculated as $\eta = \eta_0 / \sqrt{\epsilon_r} = \dfrac{377}{\sqrt{4.0}} = 188.5 \ \Omega$?
I am currently studying the textbook Microwave Engineering, fourth edition, by David Pozar. Chapter 1.4 THE WAVE EQUATION AND BASIC PLANE WAVE SOLUTIONS says the following:
Plane Waves in a Lossless ...
- 889
2
votes
0
answers
103
views
How to deduce the structure of an EM wave [closed]
Suppose we have, in vacuum, the following electric field:
$$\vec{E}(z,t)=\sqrt{\frac{2\omega ^2}{\varepsilon _0 V}}q(t)\sin\left(kz\right)\hat{x} \tag{1}$$
in my lecture notes it is stated that then ...
- 4,577
0
votes
2
answers
323
views
The role of the separation constant when solving the wave equation for electromagnetic waves & Cut off wave number
I have the following wave equation that I need help to solve via separation of variables:
$$\nabla^2 \mathbf{E} + k^2 \mathbf{E} = 0$$
Where E is the electric field and k is the wave number
Using ...
- 37
0
votes
1
answer
320
views
Can both magnetic and electric fields induce current from an EM wave?
I was reviewing a homework problem I completed for class, but I saw different explanation that contradict each other.
My teacher says that this position for the waves is optimal for maximum induced ...
1
vote
0
answers
79
views
Proof $\Delta \vec{E} = \frac{1}{c^2} \frac{\partial ^2\vec{E}}{\partial t^2}$ [closed]
Here's what I'm doing, but I'm not sure if this is correct.
Furthermore, I think $c^2$ is the speed of light, however is $c^2 = (\mu_0\epsilon_0)^{-1}$ as follow?
$$\nabla \times (\nabla \times \vec{...
- 29
5
votes
1
answer
518
views
Is this a possible derivation of the electromagnetic wave equation?
Some Background:
I've been trying to understand electromagnetic waves, how they travel, and how they're produced. After some Googling and Wikipedia(ing?) I've learned that we use the EM Wave Equations ...
- 258
0
votes
1
answer
281
views
Why is the value of volume charge density $ρ$ zero in lossy medium?
Given is the page of a book which I was studying. I was trying to study the derivation of the wave equation in a lossy medium. As I have underlined a sentence that says, "most of the case in ...
1
vote
3
answers
13k
views
Deriving the wave equation for electromagnetic waves
I'm currently referring to the wave equation derivation given in "Introduction to Electrodynamics" by David J. Griffiths. It follows something like this:
The electromagnetic wave equations are given ...
- 87
3
votes
2
answers
2k
views
Proof that $||\vec{E}|| = c||\vec{B}||$ for electromagnetic waves from maxwells equations in vacuum
Starting from Maxwell-equations in vacuum :
$$
\nabla \cdot \vec{E} = 0
$$
$$
\nabla \times \vec{E} = - \frac{\partial \vec{B}}{\partial t}
$$
$$
\nabla \cdot \vec{B} = 0
$$
$$
\nabla \times \vec{B} =...
- 297