All Questions
12
questions
2
votes
0
answers
27
views
Definition of the displacement field in classical field Lagrangian
In a BSM related paper (in appendix B), the authors use an effective Lagrangian $\mathcal{L}_{EFT}$, and define the following fields:
$$ \mathbf{D} = \frac{\partial\mathcal{L}_{EFT}}{\partial\mathbf{E}...
- 143
0
votes
1
answer
123
views
Wave propagation in inhomogeneous media
There is a problem I'm trying to solve for some time now and is about the standard (?) approximation that it is made when one tries to solve the Helmholtz equation in inhomogeneous media, that is
\...
- 11
1
vote
1
answer
112
views
Where can I find tables of the refractive index (real and complex part) or dielectric function as a function of frequency for different materials?
I need this information to do simulations for my master's thesis but I don't know if there is a bibliography or a repository on the internet with this information. They are simple materials, water, ...
1
vote
1
answer
173
views
The difference between the equation of Permittivity and Permeability in a medium
I notice that the equations of Permittivity and Permeability in a linear medium are exactly opposite of each other. One is $$\mathbf{D} \equiv \varepsilon \mathbf{E}$$ while the other one is $$\mathbf{...
- 11
4
votes
2
answers
708
views
Intuitive meaning of the permittivity and the permeability in Electromagnetism
I wonder what the correct way to intuitively understand the concepts of electrical permittivity and magnetic permeability would be.
The electric permittivity $\varepsilon$ of a medium is defined as a ...
- 974
1
vote
1
answer
201
views
Why can't $ε_r<1$ (at low frequencies)?
I've heard it said that the vacuum permittivity is the lowest possible permittivity for any substance, that no substance can have $ε_r<1$. Is this true? If so, why is this different from ...
- 389
2
votes
2
answers
1k
views
Maxwell's equations, nonlinear media, and dynamic response
Maxwell's equations in the vacuum with electric permittivity $\epsilon_0$ and magnetic permeability $\mu_0$ are given as:
$$\nabla \cdot \vec E = \frac{\rho}{ \epsilon_0}$$
$$\nabla \cdot \vec B = 0$...
- 24.8k
4
votes
2
answers
5k
views
Can relative permittivity be less than 1?
Relative permittivity shows that force of interaction in some media is 3 times less than in vacuum ($\varepsilon = 3$) for example. When looking tables of permittivity I never saw a value less than 1.
...
- 255
1
vote
0
answers
560
views
Reflection and transmission coefficients
Suppose we have a plane wave with s-polarization travelling through a medium with refractive index $n_1$ in direction $\vec{k}$ perpendicular to a surface of a dieletric with refractive index $n_2$; ...
0
votes
1
answer
1k
views
Deriving the real and imaginary parts of the complex refractive index in a dielectric medium
I have been trying to demonstrate that for a refractive index $n=n_R+in_I$ we have $$n_I=-\frac{Ne^2\gamma\omega}{2m\epsilon_0[(\omega_0^2-\omega^2)^2+\gamma^2\omega^2]},$$ $$n_R=1+\frac{Ne^2(\omega_0^...
- 4,607
3
votes
1
answer
136
views
When exactly do we substitute $\epsilon_0 \rightarrow \epsilon$ and $\mu_o \rightarrow \mu $?
If everything is embedded into vacuum, why aren't Maxwells Equations always with $\mu_o$ and $\epsilon_o$?
When exactly do we have to make the substitution $\epsilon_0 \rightarrow \epsilon$ and $\...
- 1,619
2
votes
2
answers
3k
views
Why define relative permittivity and relative permeability?
I am reading something about electomagnetic field and the first introduce the free space permittivity and permeability for the electric field and magnetic field. And later when discussing the field in ...
- 2,383