Questions tagged [optical-materials]
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Why is glass transparent?
Once I asked this question from my teacher and he replied "Because it passes light.". "And why does it pass light?" I asked and he said, "Because it is transparent.".
The same question again, Why ...
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Why are the edges of a broken glass almost opaque?
Unfortunately I broke my specs today which I used in this question.
But I observed that the edges are completely different then the entire part of the lens. The middle portion of the lens was ...
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If we repeatedly divide a colorful solid in half, at what point will the color disappear?
Suppose I have some colorful solid, which I cut into two halves (both are identical). Take the first and cut it into two parts, and then repeat this again and again. I know that a single atom doesn't ...
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Why don't opaque objects reflect light?
My sister was doing a quiz and I tried to point her in the right direction by giving her scenarios to imagine. One of the questions in the quiz was:
Which of the following objects do not reflect light:...
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Why are no metals green or blue?
Copper is orange; gold is yellow; silver, platinum and lead are white (chromatically speaking).
Why are there no metals that are blue or green?
Why do the colours of cold metals follow, more or less, ...
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Why is diamond transparent while graphite is not?
Diamond and graphite are both made of the same atom, carbon. Diamond has a tetrahedron structure while graphite has a flat hexagonal structure. Why is diamond transparent while graphite is not (at ...
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How can the refractive index be below 1 in a dielectric?
Upon checking the optical properties of different dielectrics, I found the interesting case of $Al_2O_3$. It seems to be reported with a refractive index below 1 in the infrared range of $10 - 12~\mu ...
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What percentage of light gets scattered by a mirror?
Sunlight strikes a mirror at a 45 degree angle. The vast majority of light will be reflected about the normal. Some light will be absorbed by the mirror. Some light will be transmitted through the ...
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How do non-mechanical solid-state optical switches work?
I am currently looking for a fiber-optical switch (FOS) in order to be able to change the light source of a spectrometer. As this will be used in harsh conditions, I was hoping to find a FOS with no ...
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Is the visible light spectrum from "red-hot glass" at least close to Blackbody Radiation?
Briefly, for visibly transparent materials like glass, you can see through then even while they are glowing red hot. Most glasses have plenty of absorption in the IR, so there is plenty of absorption ...
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What are the current experimental limits on the polarizability of the vacuum?
Many (all?) materials are polarizable at some level; meaning that when we apply an electric field across the material, there is an induced dipole moment
$$
\vec{p}=\alpha(\omega)\vec{E},
$$
where $\...
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Slowing down light in an opaque crystal for a whole minute
I just read about a team of physicists at the University of Darmstadt, Germany, that managed to completely slow down a beam of light that traveled through an opaque crystal (article here).
How is it ...
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What is the energy loss in total internal reflection?
In total internal reflection light inside a dense medium reflects from the boundary to a less dense medium. Since by Snell's law there is no allowed refracted ray, all energy continues along the ...
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Could a transparent frequency-altering material be possible?
I would imagine a material that is transparent but a electromagnetic wave going out will have a lower frequency than when going in (and maintaining it's direction). You could build glasses to see UV-...
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Why can't ultraviolet light pass through glass?
What factor determine whether a body behaves like a transparent object for EM waves of a particular frequency?
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Why do everyday plastic items interfere with light polarizers?
I recently bought a few pieces of linearly polarized film (the one intended for smartphone LCD screens). At first I was confused because I could not make the polarizers work as they should - no matter,...
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Why is $\textbf{D}$ the response to $\textbf{E}$?
In the text Wooten, equation 2.69 shows $\textbf{D}$ being the response to $\textbf{E}$ with $\epsilon$ as the response function:
$$
\textbf{D}(\textbf{r},t) = \int d\textbf{r}^{\prime} \int dt^{\...
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Are there yet Optical Magnetic Mirrors (OMMs) which reflect via interaction with the magnetic field?
update 2021: As the question has remained unanswered for five years and the field of optical metamaterials has advanced, I think this question can be revisited.
The most familiar mirror relies on ...
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Why doesn't infrared radiation pass through objects?
It cannot be due to Raman scattering because $1$ in $10^7$ photons are Raman scattered. It cannot be Rayleigh scattering because Rayleigh scattering of infrared radiation is very low due to the ...
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Are special relativity calcs affected by media?
Time dilation, increase in mass, Lorentz contraction calcs all involve velocity of light in vacuum. But in optical media light slows down. So what of relativity calcs in media? Do we ever need to ...
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Why does aluminium-on-glass mirror work without distortion?
I have read an article about glass (zerodur) with low thermal expansion coefficient. It is mentioned that large casts of such glass are covered with reflective layer of Aluminium and used as mirrors ...
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Does the front of a light wave always propagate at $c$ in media
Consider light moving along one dimension at the classical level. I am interested in the situation where a wave front impacts a material with some generic index of refraction $n(\omega)$, and ...
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Why are birefringence materials so rare?
By symmetry, most crystals will show birefringence. But the effect is very minute. So the question is actually, why is the birefrigence effect in most low-symmetry materials so small?
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Optical Retroreflectors: How Are the Faces So Accurately Righted?
This question is about Optical Retroreflectors (corner cubes) and how the extreme precision in their manufacturing is achieved. I suspect there is interesting basic physics involved, which is why the ...
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Difference between permittivities $\varepsilon_\text{opt}$ and $\varepsilon_\infty$?
Very often, in materials physics, we are interested in the relative permittivity at optical frequencies which is usually denoted by $\varepsilon_\text{opt}$ or $\varepsilon_\infty$.
But I'm confused ...
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Why are there direct bandgaps?
This Question has been bugging me for sometime. Some semiconductors have direct bandgaps and indirect bandgaps. So what causes a direct bandgap to occur? The physics behind ,why there are direct ...
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Can invisibility be achieved through physics? [closed]
I’ve been reading about the concept of invisibility in physics and am curious about its feasibility. We often see references to invisibility cloaks in science fiction, but what does physics say about ...
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Are there any real-world examples of refraction of light by magnetic permeability?
The question Fresnel Transmission Coefficient for Magnetic Field is interesting.
Thinking about it led me to reflect upon what little I know of the history of optics, with refraction by lenses and ...
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Does temperature affect the index of refraction?
I would like to know the physical reasoning behind the fact that temperature indeed does change the index of refraction of a certain medium.
(Is there an easy experiment for me to try this at home?)
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Meaning of circularity in phase retarder definition
A phase retarder is generally some birefringent material used to modulate the phase of polarized light. A common example is a half-wave plate, which rotates linearly polarized light symmetrically ...
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Are all fluorophores dipoles?
Lately I'm reading about surface enhanced fluorescence. In many articles I can see that fluorophores are called "dipoles". Is it because that they can be modelled by a vibrating electric dipole? Or ...
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How do optical fibres work with high critical angles?
The critical angle is given by:
c = arcsin(n2 - n1)
For a typical optical fibre, it says on the web that refractive index (n2) for cladding is higher than that of the glass core (n1) but it's only a ...
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Why does "liquid glass" putty turn cloudy when deformed?
What physical process is taking place to make it look cloudy? What's changing to make it turn back to clear over time?
While they seem pretty secretive about the exact composition, but I did find ...
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Why does optical media have different refractive indices?
Optical density is a measure of the refracting power of a medium. In other words, the higher the optical density, the more the light will be refracted or slowed down as it moves through the medium. ...
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What plastic-like materials allow IR to pass through them? [closed]
What plastic-like materials allow IR to pass through them?
Material should be solid and plastic like. Does't care if it is transparent to light or not.
IR ray is emitted by Sharp distance center so it ...
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Periodic multi-layer scattering of neutrons
I am trying to understand the reflectivity plot on slide 26 of Neutron optics,Soldner lecture.
1.Is the peak from $\theta$=0.0 to 0.4 due to total external reflection from the first upper surface?.
...
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What is the connection between the refractive index of a material and its transparency?
From my understanding, refractive index is an indication as to how the speed of light changes when it passes through a material. However a professor has asked me how would I determine whether or not ...
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Anodized aluminium reflectivity at 10.6 um
I wonder how I can model anodized aluminium reflectivity in ray tracing-based optical simulation. I know that the parts my company is using are anodized to get covered with a ~20 um (as specified) ...
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Light splitting plastic film in phone display screen
I was recently taking apart a button-press phone (like this one) and right under the glass protective screen was a thin plastic film.
This is what happens when I place it over a single dot:
As far ...
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Experimental detection of Anderson localization of light in 3D vs 2D
I have a question about the experimental realization of Anderson localization of light. I am a theorist, and have not worked much in optics, so please bear with me.
Anderson localization of light in ...
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Why does the refractive index not mirror the Lorentzian peak shape of the absorption index?
In the characterization of materials, there are many methods used: One of them is infrared spectroscopy. In a lab we saw the indices of refraction and absorption of a certain (semiconductor) solid ...
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Is there a material that allows light to pass perpendicular to the surface, but reflects at an angle?
This is inspired by Michael Steven's new video about optics.
He shows off Selenite, which has the property that light entering on one side travels perpendicularly down the crystal until it exits the ...
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How does a broadband dielectric Mirror work?
It is widely known that dielectric mirrors work with several layers of at least two materials which differ in refractive index that are layered, such that partially reflected waves interfere ...
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Diameter of a lens vs Diameter of the circular Aperture of the lens vs Aperture of the lens
I was reading about resolving power in which it is said that "a is the diameter of the circular aperture or the diameter of the lens, whichever is smaller" . So, I don't understand how are they not ...
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Is it possible to make an optical lense that is an analog to a gravitational lense?
There are many lenses that do all sorts of things. eg. horshoe lenses twist light, meta material lenses can boggle the mind.
Is it possible to make an optical lense that is an analog to a ...
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Variations in Refractive Index of Materials
It's quite a common fact that different types of glass have different refractive indices. Most sites I've found attribute these differences to variations in the 'density' of the glass, which is not ...
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Ideal surface for a perfect lens
in this physics lecture, on slide 15-16, it is found that the ideal surface for a perfect lens (which maps a plane wavefront into a perfect spherical wavefront, i.e. which makes focus all input ...
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Brewster's angle for Metal?
As metal has a high refraction index, it is possible to have Brewster's Angle for Metal when the light incident from the air? Is it possible to derive from any formula?
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What is the mechanism of transparency of EM?
What happens in transparent materials? Do their molecules oscillate with the same frequency as the EM wave and then reemit in the same direction? Or the light goes through meshes in the bulk?
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How to measure the wavelength of a laser? [duplicate]
I'm building an enclosure for a laser engraver that emits light at ~455nm. I want to be able to measure the wavelength of the light that is refracting off the item being engraved. I would want to be ...
