All Questions
Tagged with electromagnetic-radiation optics
712
questions
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26
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Is there a substance which can pass both IR and UV radiations?
I have been thinking about this for a while. A quartz prism allows UV Radiation to pass. A rock salt prism allows IR radiation to pass. Glass absorbs both.
Is there something, that is, a substance to ...
-3
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0
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20
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Is there an IR-camera-detectible color that can be the coat for a material to transfer the material heat by emitting into the space? [closed]
If we see a material it is coloured in a color that our brain could easly recognize. But when we look at it by the help of an IR camera it could also be coloured and if two materials have same ...
0
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0
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14
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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 ...
- 1
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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 ...
- 507
2
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0
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38
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Direction of propagation of extraordinary wave inside a birefringent medium
I am reading Optics by Ajoy Ghatak, in which the author explains the phenomenon of double refraction in a calcite crystal using Huygens' principle. My query is in the analysis of the case of normal ...
- 21
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26
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Solarization Spectrum
I'm looking to better understand the relation between the spectrum of the light which induces solarization in glass and the spectrum of the induced absorption.
More specifically, I'm interested in ...
- 1,538
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96
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How to compute the diffraction efficiency of a thin phase grating with arbitrary groove shape?
From Magnusson and Gaylord (1978), the wave amplitudes, $S_i(z)$, of $p$-polarized light for a thin, arbitrary phase grating are given by the equation
$$
\frac{\partial S_i}{\partial z} + \gamma \sum_{...
- 123
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1
answer
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 ...
1
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1
answer
40
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Can an optical medium be lossless and dispersive?
Occasionally, I come across the phrase "lossless dispersive linear optical medium". How can such a medium be possible mathematically? I mean the real and imaginary parts of the electric ...
- 437
11
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4
answers
2k
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Can the laser light, in principle, take any wavelength in the EM spectrum?
Can the laser light, in principle, take any wavelength in the EM spectrum? I don't think there is what prevent this in principle, right?
- 959
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1
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47
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Is there a way to use the optical transfer-matrix method to determine the absorbance of each layer in a multilayer stack?
I've implemented the transfer-matrix method to determine the the transmittance and reflectance of a multilayer stack of thin films.
I know that (ignoring scattering) the absorbance of the entire stack ...
- 123
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43
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Spherical laser beam terminology
I am currently seeking the correct terminology for a beam that expands linearly from a fixed point, resulting in its wavefronts forming spherical surfaces. However, the beam does not expand in all ...
- 153
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0
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35
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What happens when a linear polarized EM wave encounters a perpendicular mesh of wires (which are electrically connected)?
Assume a radio wave with wavelength 1 m is traveling in the negative z direction when it encounters a grid of closely spaced wires (say, 10 cm separation) laying in the xy plane, with each wire ...
- 93
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0
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28
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How does parameters of the constitutive relation of electromagnetic media be constrained as for chiral, nonreciprocal or loss media?
The constitutive equations are:
$$
\bf D =\varepsilon E +\xi H \\
B =\mu H + \zeta E
$$
Why, when the media is nonreciprocal, the parameters $\xi$ and $\zeta$ only can take the real part equals zero,...
- 13
3
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4
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328
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A question about circularly polarized light
At work, a senior colleague thinks that circularly polarized light does not exist. My problem is that we both work on a project involving polarized light. In some occasions, I would like to point out ...
- 33
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0
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37
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How to measure light intensity in a room?
Does anyone know how I would go about measuring the light intensity in a room? I'm not interested in knowing the lux reading, I would like to measure the $W/m^2$ due to thermal radiation in my ...
- 31
2
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4
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133
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Reflection due to wave nature of light
In my high school, I am studying geometrical optics. I studied why smooth surfaces like mirrors form an image of an object but rough surfaces like a wall don't (due to regular reflection and irregular ...
7
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5
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14k
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Light waves can't have a wavelength
The wave nature of light comes from Maxwell's equations. More precisely, the two wave equations that come from them:
$$\Delta\vec{E}=\mu\varepsilon \frac{\partial^2\vec{E}}{\partial t^2}\\
\Delta\vec{...
- 267
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1
answer
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)}{...
- 267
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46
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How can a greater than 1 reflectance coefficient be explained in $\rm SiC$-$\rm SiO_2$ interface?
I ran a simulation using the Transfer Matrix Method to plot the R,T and A curves for a SiC->SiO2 interface. There's a region of incident energies where the |r|^2 I get is higher than 1 and the ...
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1
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32
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Absorption and emission spectrum
I was wondering how do you see a spectrum when light is passed through a substance. Like most of the substances we use are opaque, so how does light pass through them without being reflected? Also ...
- 11
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1
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37
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Ray separation in waveplates
In a birefringent medium, the ordinary and extraordinary rays have different Pointing-vector directions and, therefore, different propagation directions, since the direction of the Poyting-vector ...
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1
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51
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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 ...
- 531
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32
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Intensity of non-monochromatic electromagnetic radiation
The intensity of a monochromatic electromagnetic wave is given by
$$ I \equiv \langle S \rangle = \int_{t_0}^{t_0+T}c\epsilon_0 E_0^2 \cos^2(kx-\omega t) \text{d}t = \dfrac{c\epsilon_0}{2}E_0^2. $$
...
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1
answer
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 ...
- 11
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2
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59
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Is sky still blue when the line-of-sight is perpendicular to the sunlight ray?
We model molecules in the atmosphere, excited by sunlight, as tiny dipoles, which radiate as ~ $\omega^4 \sin^2 \theta$, where $\omega$ is the angular frequency and $\theta$ is the angle between line-...
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0
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34
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QFT view of lower light speed of light in medium [duplicate]
In classical EM theory, if we have a medium whose dielectric coefficient is independent of wavelengths (suppose we filter the incoming signal to a certain frequency band), then the waveform gets to ...
1
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1
answer
45
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Why do we see objects with a given color?
I'm currently studying Electromagnetic Optics, and I don't quite understand the (classical) process through which we perceive an object with a given color. From my understanding, I'd make a ...
- 1,616
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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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28
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How does an electromagnetic wave behave when it enters a medium with refractive index less than unity?
From what I am able to find, the phase velosity of the wave exceeds c, but the group velosity remains less than c. However, why does the wave form wavepackets after entering a medium with refractive ...
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1
answer
45
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Imhomegenous Wave Equation: Possible Born and Wolf Error
My concern involves the following lines from Principle of Optics (Born and Wolf 7th ed, 60 year anniverary, Section 1.2 pg 11). I fail to derive these equations 5,6 exactly.
$$
\begin{align}
\nabla^...
- 948
2
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1
answer
48
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Physics behind Lambertian reflectors
Most ordinary surfaces are near Lambertian diffuse reflector, i.e. a small local radiates most strongly at norm then attenuates by cosine law when one gets to the tangentials. However this seems hard ...
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0
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22
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Understanding and researching with Spectroscopy
I am very new to physics so don't know a whole lot yet, so please correct any incorrect vocabulary you may find. Papers that are easy for beginners to understand are also very welcome!
Context:
I am ...
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6
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4k
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Why does white light appear white?
When I think of white light, I'm imagining a combination of all 7 colors of light but I believe that since light has wave nature I can say that at some point that the probability density of red light ...
- 93
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104
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The speed of light in medium with different frequency
We know that the speed of light in vaccuum can be expressed as $c=\frac{1}{\sqrt{\mu_0\epsilon_0}}$ and thus the speed of light in vaccuum is thus $$v=\frac{1}{\sqrt{\mu\epsilon}}=\frac{c}{\sqrt{\...
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1
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50
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Huygens Light Theory using Spheres and Miller's recent discovery?
Huygens writes in "Treatise on Light" a theory that propagation of light through the aether can be explained using Spherical waves emanating from every point and they interfere. Miller ...
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1
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37
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Struggling with interference [duplicate]
I was reading the book optics by zajac and hecht. It was a nice one until physics optics, i got that interference becomes when the light is coherent and monochromatic, and it is the superposition of ...
3
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1
answer
158
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Infinite reflection inside a glass loop
If you had a loop made of completely transparent glass (or other material), in the shape of a donut; think atomic collider (but probably not needing to be so large :) ), and you introduced light from ...
0
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2
answers
131
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Determining Gaussian beam parameters of a laser
The intended output of many lasers in laser scanning is Gaussian. At distance $z$ from the waist, the radius of a Gaussian beam is calculated as
$$w(z) = w_0 \sqrt{1+(z/z_R)^2},$$
where $w_0$ is the ...
- 153
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0
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28
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For Rayleigh scattering, what is the phase difference between the incident field and the scattered (or reradiated) field?
I am asking within the context of electromagnetic theory. Much of the discourse I could find in the literature was more focused on the phase differences between the scattered fields of various ...
- 21
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2
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63
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Which factors determines whether a photon is absorbed? [duplicate]
After some research, I figured out that all EM waves/photons are absorbed by atoms by exciting an electron from an orbital to an other. However, atoms emit only certain EM waves with specific ...
- 167
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1
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47
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Doppler broadening upon reflection from liquid interface
I just came across the question "Why are the surfaces of most liquid so reflective?", in which the author asks how the surface of a liquid gives rise to a mirror image, even though it ...
- 3,260
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1
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92
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Energy of Monochromatic Beam of Light
A monochromatic beam of light has energy
$$ E_{\text{beam}} = N \hbar \omega, $$
$ N $ being the number of photons in the beam and $ \omega $ their frequency.
Another way to evaluate this energy is ...
1
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1
answer
61
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Dielectric wave guides vs metallic wave guides
I have a couples of questions regarding wave guides. First of all, why are dielectric wave guides better than metallic wave guides for wavelengths in the visible spectrum? Also, for non-ideal metallic ...
- 31
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1
answer
91
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What is the physics behind a non-zero beam waist in Gaussian Beams?
I have been doing some deeper reading on optics out of my interest and one of the most important differences between ray and Gaussian optics is the existence of a non-zero beam waist when a laser beam ...
1
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0
answers
51
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What is the connection between Ray (Geometric) optics and Electromagnetic theory optics in fiber optics?
I am currently reading about fiber optics and wave propagation in fiber optics and encountered the following part of Gerd Keiser's Book :
according to the diagram shown, its a general case when the ...
1
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3
answers
72
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Wavelengths of light outside our solar system
The question might have been asked before. Our Sun's rays decompose into 7 elementary colors by using a prism or spectrometry. Can the the colors (their number and wave length in the spectrum ) be ...
- 1,032
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1
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45
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Is it possible to optically threshold the amplitude of light waves - lower amplitude passes unaffected, higher amplitude gets lowered?
One can certainly create a digital circuit the achieves this - is it possible to do it in a purely "optical" manner?
If not with light waves, would it be possible with any other type of wave?...
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46
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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}$...
- 155
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1
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51
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How does wetting cotton increase its UV transparency?
Anecdotally, a dry cotton T-shirt prevents sunburn better than a wet one.
This has also been measured (Gambichler et al., "Influence of wetness on the ultraviolet protection factor (UPF) of ...
