All Questions
Tagged with optics electromagnetism
596
questions
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How to use dipoles to enforce the boundary conditions for a spherical dielectric with complex permittivity
I want to impose an electric and magnetic field on a spherical dielectric of radius $ R $ and relative permittivity $\epsilon_r=\epsilon'+i\epsilon''$. Say the fields are slowly-varying (like a plane ...
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2
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123
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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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1
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31
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What is the relation between the Faraday effect and the Zeeman effect?
The Faraday Effect basically says that certain materials under a magnetic field have different indexes of refraction for right and circular polarized light. Linear light which is a superposition of ...
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1
answer
55
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Permittivity real and imaginary parts with similar value possible?
Here's the context; I'm studying biological tissues that are supposed to behave like dielectrics. Using the modified cole-cole equation for theoretical predictions:
$$\tilde{\varepsilon}_r (\omega )= \...
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1
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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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1
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52
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Confusion regarding phase
As far as I know about phase if the phase difference between two waves is positive, the former is leading..and the latter is lagging. Then why has D J Grifith stated this?
If the phase of the magnetic ...
2
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2
answers
45
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How should I calculate the TE and TM modes on an anisotropic/uniaxial slab waveguide?
I want to find the equations governing the TE and TM modes on the following three-layered slab waveguide:
I know how to use the Helmholtz equation and solve for the boundary conditions on normal ...
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1
answer
33
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Light acceleration method using inhomogeneous material mediia
Some time ago I posted this question but I reckon it was too vague. Nontheless, I've been working on it and I've come up with some interesting conclusions. My question is: can light be subject to an ...
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22
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Surface plasmon polariton filling the gaps
Why does the angle of incidence on a DPS(positive electric permeabillity and magnetic susceptibillity)material and a SNG(1 of $\epsilon$ and $\mu$ positive)material have to be close to 90 degrees to ...
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1
answer
44
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Are temporal coherence (for classical EM waves) and quantum coherence related concepts?
For my wave optics class, I was taught that the temporal coherence of a light source is the average time interval for which the phase of that light is predictable, after which the source will undergo ...
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1
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162
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Intensity and complex electric field
I have come across an issue with the use of complex electric and magnetic fields that I just cannot quite figure out. I will lay out my thought-process and I would like to know if and why it is wrong.
...
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25
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Meaning of negative frequency in nonlinear susceptibility?
When I am learning the nonlinear optics, for cases like difference frequency generation and optical rectification, the second order susceptibility tensor can take the form $\chi(0;\omega,-\omega)$. ...
2
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2
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Why is a monochromatic wave temporally coherent for all time delays $\tau$?
I've been learning about coherence of waves and the Wikipedia page on says a monochromatic electromagnetic plane wave is coherent because:
A wave containing only a single frequency (monochromatic) is ...
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1
answer
78
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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 ...
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2
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53
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Amplitude of light in double slit experiment
While reading about double slit experiment I have found no article where the amplitudes of light at the board ( on which light falls) is calculated . Only the fringe width and intensity ratios are ...
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26
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How can Fresnel's transmission coefficient be nonzero in Total Internal Reflection?
I'm working on a problem in which a wave is moving through a transparent medium of refractive constant $n_i$. It then reaches the interface of said medium with another one of refractive constant $n_t&...
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Why the dielectric permitivity matrix of lossless media is symmetric?
I am studying optics and I met a strange statement in the section 2.3.4 (page 34) of Fundamentals of Nonlinear Optics by Peter E. Powers and Joseph W. Haus.
The relationship between $\vec{D},\ \vec{E}$...
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Ambiguities in optical waveguide modes
While studying concept of slab waveguide mode, I got stuck on some problems.
In textbook(Yariv chapter 3 pg 112), for guided TE modes it tells that the mode function
is taken as
which means that the ...
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5
answers
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Light waves can't have a wavelength
The wave nature of light comes from Maxwell's equations. More precisely, the two wave equations that come from them:
$$\Delta\vec{E}=\mu\varepsilon \frac{\partial^2\vec{E}}{\partial t^2}\\
\Delta\vec{...
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1
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47
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Why are Fresnel coefficients not symmetric?
When talking about reflection, we have the following coefficients for the electric field:
$$r_{\perp}=\frac{n_1\cos(i)-n_2\cos(t)}{n_1\cos(i)+n_2\cos(t)} \\ r_{\parallel}=\frac{n_2\cos(i)-n_1\cos(t)}{...
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2
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Why total reflection happens at only 1 angle?
The critical angle can be intuitively understood by Snell's law.If the incident medium has a bigger diffraction index than the refracted medium then according to Snell's law the refracted ray will be ...
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Why isn't the original EM wave in a beam of light in a medium not still detectable from a distance as if it were moving at the speed of light?
I'm learning optics and I've been told that the reason light slows down in glass is because the Electromagnetic field of a beam of light interacts with and accelerates charged electrons in glass ...
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Why does the energy (and thus frequency) of a photon entering glass stay constant if some is used up to accelerate electrons and slow down the light?
I'm learning optics and have been told that when light enters a medium (e.g. glass) and slows down the frequency of the light stays constant while it is the wavelength which is reduced. The ...
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107
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Units of Poynting vector (or flux of energy) and field intensity
In optics, the Poynting vector of an EM wave is
$$\boldsymbol{\mathcal S}=\frac{c}{4\pi}\,\mathbf E\wedge\mathbf H$$
and if I am not mistaken its units in the SI system should be $\mathrm{W/m^2}$, or ...
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19
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Metals behaving as dielectrics for certain frequencies
I'm studying the complex refractive index of material media, which is given by:
$$n_c=n+i\kappa$$
where $n$ is the refractive index and $\kappa$ is the absorption index. I interpret this as though $n$ ...
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26
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Physical interpretation of a dielectric's absorption curve
A given dielectric will behave as an absorbing medium for some frecuencies (those near one of the material's several resonant frequencies), whilst it will behave as a non-absorbing medium for the rest ...
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17
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If a material is homogeneous in $\varepsilon$, can this material be made of different atoms?
I'm currently trying to derive the microscopic expression for the dielectric constant of a material following my proffessor's notes. However, he admits that, even though he assumes $\varepsilon=...
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24
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Trouble deducing a dipole's scattering cross section (optics)
(I've already visited this post but it begins precisely with the formula I'm trying to derive). I'm trying to deduce the scattering cross section for an electron bound to a nucleus in the far field:
$$...
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2
votes
2
answers
84
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Dot product in optics
(Before marking this question as a duplicate, please consider I've read this post but it I didn't find the answers to it quite satisfactory regarding my doubt).
I'm trying to derive the expression of ...
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31
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Effect of incident angle on wavelength of transmitted wave for normal polarisation?
In my electrodynamcis assignment I'm being asked to derive the wavelength of a normally polarised wave transmitted through a glass/air interface as a function of $n_1$ (the refractive index of the ...
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6
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871
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Can circularly polarized light induce magnetization?
In optics, we usually consider a non-magnetic medium where the magnetization $M$ is zero, while the polarization P is proportional to the electric field $P=\epsilon_0\chi E$. $P$ is induced by some ...
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1
answer
90
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Reflection coefficient: Acoustics vs Mechanics
I recently tried to derive the reflection coefficient $R$. This is not a complicated task, however after making some literature research I found two derivations which arrive at seemingly different ...
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2
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47
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Calculating magnetic field from polarized electric field
My question is very simple: let a plane monochromatic electromagnetic wave's electric field be:
$$\vec{E}=\begin{pmatrix}0\\1\\-i\end{pmatrix}e^{i(kx-\omega t)}$$
as you can see, the electric field is ...
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1
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123
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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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30
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Polarization of electric field and its effect on the Poynting vector
To preface, I've little experience with optics. This is a very use-case specific project I'm undertaking. So, if there are any improvements in my method, I'd appreciate it!
I'm working with the vector ...
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1
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54
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Understanding TE and TM modes in plane harmonic waves
I've been researching the concept of Transverse Electric and Magnetic modes, and I've found in this Wikipedia article that TE, for example, is defined when there is just $H$ in the direction of ...
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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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28
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Optical properties of non-Newtonian fluids
I'm interested in understanding the distinctions between non-Newtonian fluids and regular Newtonian fluids regarding their optical properties, including refractive index, nonlinear optical behavior (...
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12
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Question about calculating electric susceptibility as a function of temperature
I am trying to calculate the electric susceptibility as temperature changes. From a textbook, [1], the equation is: $$\chi (\omega) = \frac{Ng_2A_{21}\pi c^3}{g_1\omega_0^3}\left\{\frac{1}{\omega_0 -\...
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48
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Stokes' vectors and quaternions
About a month ago, I was presented in my Optics class (classical and electromagnetic optics, to be more precise) the representation of partially polarised light through Stokes' vectors. Now, it ...
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2
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71
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Radiation through optical windows
Edit: I have tried answering this a different way since posting this, see my newer answer below.
Problem I'm interested in solving: How much radiative heat load is entering the system through optical ...
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1
answer
26
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The expression of photocurrent
Consider an electro-magnetic field represented in phasor notation $E_0e^{-jwt}$ incident upon a photodetector/photodiode, what is the expression of the generated photo-current $I(t)$? Here $E_0e^{-jwt}...
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What should be minimum width of slit for interference pattern to occur in a single slit experiment? [duplicate]
When two slits produce an interference pattern, and one slit is closed, then the interference pattern disappears. Why? As one-slit interference is still possible. What should be the measurements of ...
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22
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What is the relationship between the energy absorbed and reemitted by an atom?
What is the relationship between the energy absorbed and emitted by an atom with the model of Lorentz?
In the Lorentz model of an atom, we have that, using the effective cross-sections we might get ...
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1
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51
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Linear momentum of an EM wave
In my optics textbook, the derivation of the expression for the linear momentum of a plane wave shocks me as rather sloppy, but I don't know if I should be so shocked. It goes as follows:
Let a plane ...
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2
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1
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79
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Differences in the direction of energy and wave propagation in anisotropic media
I have been studying how light behaves in dielectric and conductive media, and now I was about to study it in anisotropic media. The introduction to the subject is: "From Maxwell's equations it ...
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1
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50
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Huygens Light Theory using Spheres and Miller's recent discovery?
Huygens writes in "Treatise on Light" a theory that propagation of light through the aether can be explained using Spherical waves emanating from every point and they interfere. Miller ...
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2
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156
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Graphical interpretation of complex electric fields
Before anything, I have read similar questions here but still something doesn't click perfectly, so I'll try to describe so.
My doubt is essentially that I have always thought $\vec E$ in the context ...
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3
votes
1
answer
102
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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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3
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135
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Divergence of $H$ Maxwell equation
In the below screenshot from this paper (link below), why is the 2nd Maxwell equation ($\nabla \cdot H = 0$) not automatically satisfied when the 4th Maxwell equation is satisfied? I don't understand ...
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