All Questions
39
questions
3
votes
2
answers
134
views
Why is $c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}$?
I'm sorry if this is a duplicate but I didn't find my answer. I'm currently studying maxwell's equations and I know that by comparing the wave equation for either the magnetic or the electric field
\...
- 33
8
votes
2
answers
5k
views
At what speed does information move through the atoms of a rigid object?
How fast does information travel on particles? I thought if you move a iron bar from one end it would take the speed of sound to move its other end. For example, theoretically if you hold an iron bar ...
- 97
0
votes
1
answer
59
views
Relativistic Effects on Electromagnetic Wave Propagation
So for a recent lab I had to calculate the length of a conductor by measuring the time it took a signal to reflect off of the open end. I used the very simple principle of $v=st$ and, knowing that the ...
- 1
6
votes
3
answers
743
views
When designing antennas which speed of light should be used?
When calculating "antenna element length" should we use the speed of light in the "medium between transmitter and receiver (antenna)" or the speed of light in the "element ...
- 613
1
vote
2
answers
104
views
Speed of EM Waves
We know that for electromagnetic waves, according to Maxwell's Theory
$$v=\frac{1}{\sqrt{\mu\epsilon}}$$
Now consider an opaque object like say Gold. It has a particular value of permittivity and ...
2
votes
0
answers
102
views
Why does refractive index increase with concentration of the medium?
I learnt that lights decrease velocity in a medium during absorbance and emission of its energy in the charged particles in the medium. From the Beer's law, I read that absorbance is directly ...
- 21
8
votes
3
answers
1k
views
Why does the wave velocity of EM signals in a wire depend on the insulator's permittivity?
I'm in an electromagnetism class and struggling with a concept. The textbook derived several equations which state that the wave velocity of an electrical signal in a transmission line depends on the ...
- 205
1
vote
1
answer
64
views
Frequency of EM waves
When light travels in air, all the component frequencies of light travels with the same velocity $v_{air} = 1/\sqrt {\epsilon_0\mu_0}$ (where $\epsilon_0$ is independent of frequency. Then we say that ...
- 453
1
vote
0
answers
28
views
Modeling curved light in media with "complex" indices of refraction
I've written an algorithm to solve the Time Difference of Arrival (TDoA) localization problem, using Bancroft's method (see). Given the coordinates of $n$ nodes in ...
- 799
0
votes
2
answers
131
views
Are there materials that just change the speed of light?
Maxwell's equations in medium without charges read
\begin{align}
0&=\nabla\cdot D\,,\\
0&=\nabla\cdot B\,,\\
0&=\nabla\times E + \dot B\,,\\
0&=\nabla\times H - \dot D\,.
\end{align}
...
- 1,291
0
votes
1
answer
82
views
Can we slowdown speed of photons? [closed]
Can we slowdown speed of photons or light? If we slowdown the speed of photon can photon give us mass?
15
votes
6
answers
6k
views
Why are red and blue light refracted differently if they travel at the same speed in the same medium?
When I look at Snell's law
$\frac{\sin\theta_2}{\sin\theta_1} = \frac{v_2}{v_1} = \frac{n_1}{n_2}$
I don't see any reference to wavelength.
If red and blue have the same speed in the same medium, why ...
1
vote
0
answers
54
views
In anisotropic media, is there a speed of light tensor like there is a refractive index tensor?
Lets say we have an homogeneous anisotropic medium where $\tilde\mu_r=\tilde\epsilon_r$ so we don't have to worry about polarization effecting anything. As such, the refractive index can be simply ...
- 780
4
votes
1
answer
650
views
Does phase velocity or group velocity change when light enters a new material? Contradictory sources
I'm so confused. I've read in this book (page 28) that group velocity of light can exceed $c$ in certain gases. However a lot of people online and in the forums say that phase velocity can exceed $c$.
...
- 143
-1
votes
2
answers
619
views
Speed of light and wavelength
Does the speed of Electromagnetic wave depend on its wave length? For vacuum I'm aware that it's a constant $c=\frac{1}{\sqrt{\mu_o\epsilon_o}}$. Similarly can we say speed of light in any medium is a ...
- 1,161