All Questions
Tagged with electromagnetism refraction
122
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Diffraction when the wavefront is not parallel to the plane
I am studying Feynman's chapter on the origin of the index of the refractive index (see this link).
If I am not mistaken, what he does is to prove that when a wave enters a medium (modelled as a ...
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Most generic form of refractive index tensors
The refractive index of a material is in general a $3x3$ tensor (as in the case of birefringent crystals). From literature, it seems that in the case of transparent crystals, this tensor is in general ...
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Inconvenience of speed of light in optic fiber
As far as I'm concerned, optic fiber is great in order to transport information quickly using light. Since light needs to undergo total internal reflection every single time it hits the walls of the ...
- 1,616
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Why total reflection happens at only 1 angle?
The critical angle can be intuitively understood by Snell's law.If the incident medium has a bigger diffraction index than the refracted medium then according to Snell's law the refracted ray will be ...
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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}...
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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
\...
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Microscopic model of complex refractive index
In my Electromagnetic Optics class, we tried to reconcile the microscopic (optical) properties of matter with its macroscopic counterparts, and one of the most challenging properties is the (complex) ...
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On the (variable?) nature of $\epsilon_0$ and $\mu_0$
In electromagnetism, the electric displacement field D represents the distribution of electric charges in a given medium resulting from the presence of an electric field E. Its relation to ...
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Can the refractive index of a medium be negative?(<0)
Recently I was asked in a test what would happen if the refractive index of a medium was negative. Is it possible really? The refractive index is the ratio of the speed of light in a vacuum and ...
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How to derive the effective permeability for split ring resonator?
in Pendry's 1999 paper "Magnetism from Conductors and Enhanced Nonlinear Phenomena", he give the formula of effective relative permeability $mu_r$ of split ring resonator (SRR) which is one ...
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Phase jump at medium border with EM wave
I have been reading a book about electrodynamics and I have stumbled upon the following matter which is, to me , contradictory. When the electromagnetic wave changes medium, it is subject to certain ...
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Effective Refractive index of a mode less than that of the cladding refractive index?
Can the effective refractive index be less than the cladding if the waveguide width is very small. For example for the case of a ~100 nm waveguide.
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Help with dispersion relations for EM waves in anisotropic dielectric materials
I am really struggling to understand the following dispersion relations which we derived in class.
For an electric field in the z-direction, we have:
$$k^2_x + k^2_y = \frac{\omega^2}{c^2}n_z^2\tag{1}$...
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How to use the boundary conditions of electromagnetic waves to derive the refraction law of light?
In my book it says we can use the boundary conditions of electromagnetic waves to derive the refraction law of light. How to derive it?
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How to increase the angle of light (without going from a higher to lower index of refraction)?
I would like a device to spread out/increase the angle of rays in a light source. In other words, I would like to reproduce the behaviour of light traveling from an area of higher to lower index of ...
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When I see a rainbow in the sky, is the full EM spectrum included? does it form a disc and not just a circular arc?
If you could actually see every part of the EM spectrum from a rainbow, would the circle be completely filled in? and would it also extend further outwards from the visible spectrum?
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Simulator to simulate the intereference between light and the wave produced by an electron driven by the light
When an electromagnetic wave reaches an electron the electron will oscillate creating it's own electromagnetic wave which will interfere with the original electromagnetic wave. I am looking for a free ...
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Mass density of photons in a refractive medium
The effective mass density of photons in a vacuum $\rho^{vac}_M$ is related to the photon energy density $\rho^{vac}_E$ by
$$\rho^{vac}_M=\frac{\rho^{vac}_E}{c^2}.$$
Is it true that the mass density ...
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Photon energy-momentum relation inside a material [duplicate]
I understand that the speed of light in a medium like glass, $c_n$, is reduced by the refractive index $n$ so that we have:
$$c_n=\frac{c}{n},$$
where $c$ is the speed of light in the vacuum.
Is it ...
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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 ...
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Is $n=\sqrt{\mu_r\varepsilon_r}$ always true? even with complex value?
I have trouble deriving a supposedly "well-known" equation used in condensed matter physics:
$$n^2=\mu_r\varepsilon_r+\frac{i\mu_r\sigma}{\varepsilon_r\omega}$$
I'm sure that $n$ and $\sigma$...
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Do any of the color bands in a rainbow contain an electrical charge relative to clouds that might explain a photo of lightning striking a rainbow?
Caveat: While I am not a physicist myself, I am extremely interested in physical phenomena. I am well versed in electrical theory, and I am aware of the attraction between the bottoms of clouds and ...
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398
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Deriving the focal length of a graded index lens (GRIN)
I want to find a closed expression of the focal length of a graded index since I don't manage to find any on the internet. I already checked this out: Determining the focal length of a gradient index ...
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What are the physics behinde reflection and refraction of electromagnetic wave at a dialectric surface?
I have understood the most of the equations that lead to the Fresnel-Equations from electromagnetic waves and Maxwell equations. But not enough to understand what is happening. So I don't ask for an ...
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Decoherence of a laser beam via oil emulsion
This is sort of a followup to an earlier question that I posted regarding how to destroy the temporal and/or spatial coherence of a laser beam. It was suggested to me that I could use a rapidly ...
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Strength of electric field needed to observe noticeable effects on refraction in water
I was looking into the mechanism behind refraction and stumbled upon a Fermilab video explaining it has to do with the electric fields of the particles in the medium interacting interacting with the ...
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Analysis of the reflection in metal
In order to solve the reflexion in a material with a complex index the solution I've found on textbooks is to define $\hat{n}\cos{\phi}:=a+bi$ where $\hat{n}=n_r+n_ii$ is the complex index and then ...
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What does the wave created during refraction look like?
People always describe refraction as light stimulating the electrons in the glass, which create their own light, which interferes with the original wave. They always say “the math is too complex, but ...
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What does the wave look like during refraction?
For example, in this image,
It shows the wave contract and shorten the wavelength. Is this actually what light looks like in a denser medium or is it more like the wave is phase shifted back ...
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Is there a wave equation describing electromagnetic waves in materials?
Solutions to the usual wave equation for electromagnetic waves have the property that wave components of different wavelengths travel at the same phase speed $c$, so no dispersion occurs.
What I ...
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