All Questions
Tagged with optical-materials optics
162 questions
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Ideal refractive index of a thin film coating
My professor wrote that the refractive index of a thin film when we do a coating of it (say on glass to make them non reflective or anything) should be
$n_f = \sqrt{n_1 \cdot n_3}
$
Why should it be ...
- 11
0
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0
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14
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How does an optical interrogator work?
Could someone explain the principles behind an optical interrogator?
I know that it is currently used to demodulate signals from FBG sensors, however, I am curious about the intrinsic workings and ...
- 57
4
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4
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297
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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 ...
- 79
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1
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35
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Linear-array diffraction beam splitter
This question is composed of two parts. The first is about the grating equation. The second is about a particular software used for diffraction gratings.
The grating equation is
$$
\sin(\theta_m) = \...
- 284
1
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1
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49
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Thin Lens in different media
I have been given an equiconvex lens (of given focal length), placed on a plane mirror, with water between the lens and the mirror.
An object has been placed at a certain distance and I have been ...
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25
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What is meant by optical density?
I’m trying to research about optical density for a school task, but the definitions online are confusing me.
From what I’ve gotten, optical density is:
how much the intensity of light is increased or ...
1
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0
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49
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Material that Increases Angle of Incoming Light
Snell's law states that light refracts when entering a substance and refracts back to its original angle upon exit. This is shown in the diagram below from this webpage.
I was wondering if there are ...
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1
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1
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52
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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 ...
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2
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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 ...
- 922
4
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1
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113
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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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0
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41
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Mixed configuration of magneto-optical kerr effect
Typically there are three types of magneto-optical Kerr effect experiments: Polar, longitudinal, and transverse. These three geometries yield very different results regarding what is measured (...
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57
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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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122
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Why can you not create a LED equivalent by illuminating a colored plastic casing?
I would first like to apologize if this is a dumb question.
I understand the physics of color sufficiently well. You have an incoming photon that intercepts an electron on the atom, the electron gets ...
- 165
1
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0
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32
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Knowing the optical path difference, how do I calculate the resulting image?
Let's say I'm taking a picture through a cube of some material where the index of refraction varies in a known way, such as a GRIN lens. I can calculate the optical path difference as a function of ...
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-1
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1
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Transmittance of one material through a multilayer
Good morning,
I have the transmittance and the reflectance spectrum of PET (Polyethylene terephthalate) and I also have the transmittance and the reflectance spectrum of PET + Copper (50 nm). I would ...
- 31
0
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1
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40
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What is a true delay line and is there possibly a false delay line?
I'm reading "Silicon nitride passive and active photonic integrated circuits: trends and prospects" and one of discussed application of $\rm SiN$ is "true delay line". All the ...
- 3,074
1
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1
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64
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Do mirrors (with metal surfaces) show TIR (Total Internal Reflection)?
[Not a duplicate! Also, the answer to a similar question was unsatisfactory]
I was digging into why we don't use mirrors in place of fibre optics cables. Majorly, the answers were as follows:
It's ...
- 155
4
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1
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1k
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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 ...
- 155
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0
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300
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In a uniaxial crystal, what determines the optical axis, extraordinary axis, and ordinary axis?
In a uniaxial crystal there is an optic axis, an extraordinary axis, and an ordinary axis. The optic axis is not the direction in which we plan to propagate light. The light is propagating in a ...
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1
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75
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What happens when screen is not placed where Image is focused but elsewhere?
When we try to form a real image on a screen by a convex lens, we place the screen at a distance where the image is focused. But if we try to place the screen at a distance less than the distance ...
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1
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1
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64
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Why are things reflective, absorbent, transparent etc? [duplicate]
What determines whether a material reflects, absorbs or transmits a certain wavelength of light? Just a layman's question.
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2
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318
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Why does light either get reflected, absorbed, or passes through a surface or obstacle?
For each of these 3 cases, I'm having trouble understanding...
If light is reflected, does that mean that there was not sufficient energy by the photons to excite the electrons of the surface to ...
- 195
2
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1
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44
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Why does (oxidized) aluminum have a diffuse optical appearance?
Unoxidized aluminum has a shiny appearance like typical metals. However in air aluminum rapidly oxidizes, giving it a more diffuse appearance (or bidirectional reflectance distribution function). ...
- 143
1
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1
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152
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What difference between metallic reflection and polished/mirror reflection [closed]
At the moment I am studying materials in raytracing (I am writing my own personal project)
I found out that there are several types of reflections.
I read this article from wikipedia:
https://en....
- 11
1
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1
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46
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Are there everyday materials that change color, depending on illumination spectrum?
Initially I wanted to ask this exact question about color change due to "white" light source spectrum change, and the accepted answer satisfies me fully.
However the answer says that most of ...
- 3,074
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2
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190
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Why do non-linear optical effects occur?
Why do non-linear optical effects occur? Why do the materials respond differently at high intensities and at some resonant frequencies?
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1
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1
answer
193
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Difference between seed and pump in chirped pulse amplifier
What is the difference between to seed an optical amplifier (such as Chirped Pulse Amplifier) and to pump it with a laser source?
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3
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2
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427
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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 ...
- 1,329
3
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1
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550
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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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0
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486
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What are good materials to diffuse/scatter 850nm infrared light?
I want to properly light up a room with an IR Illuminator, but most illuminators lack diffusion, therefore shadows are especially sharp and bold. Since IR rays don't behave like visible light rays, it'...
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1
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132
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Why do efficient blue emitters (LEDs,OLEDs, quantum dots) take much longer to discover than red and green emitters?
For example, it took over 3 decades to create efficient blue LEDs in the lab after the red and green leds were discovered. For OLED displays as well, the red and green pixels are phosphorescent oleds ...
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1
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1
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259
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How does reflectance change with wavelength? [duplicate]
Sorry if this is an easy question, I am new to physics and this field.
I have a question about reflectance which i believe to be "effectiveness of reflecting radiating energy"
My goal is to ...
- 11
0
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1
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73
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Why do some anti-reflective (or anti-glare) lenses use layers of materials with alternately very high and very low refractive indices?
Some specials lenses like this (or coatings on them) try to minimize the refractive index, or the change thereof, or at least make the change very gradual.
But others apparently do the exact opposite, ...
- 4,709
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1
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70
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What formalism is used to model thin film optical coatings that function across a range of angles of incident light?
Thin film optical coatings [0] are atomically/molecularly thin layers of material applied to a substrate with the intent of affecting the optical properties of the substrate. For example, magnesium ...
- 21
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0
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36
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How to get rid of unnecessary signal in Photoluminescence Spectroscopy?
I am having some issues figuring out have to get rid of laser residues (might be) or scattering from the setup itself (please see attached pic).
In the lab, we have AUREA PIXEA 405nm laser, Horiba ...
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1
answer
392
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How can we generalize the definition a non-linear media?
According to the definition: Nonlinear media are dielectric materials whose polarization density changes nonlinearly if a strong field is applied to them. If the field is small the nonlinear terms ...
- 1,408
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0
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21
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Calculating magnification of a put together telescope
My objective lens has focal length of 50 cm and I am using a 10x eyepiece (I don't have anymore info). I am not sure how to calcuate the focal length of eyepiece. How do I find the total magnification ...
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2
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0
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178
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What can be the possible causes for variation in stress-induced birefringence in an isotropic material?
Birefringence is the phenomenon of a material having a refractive index that depends on the polarization and propagation direction of light. When an unpolarized light passes through such a material, ...
- 21
3
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5
answers
619
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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 ...
- 1,558
4
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1
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61
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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 ...
- 465
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0
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125
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Hi everyone, could anyone help me understand how two cylindrical lens can be used to form a laser sheet?
If you look at the below link under 'Laser Sheet',
https://www.edmundoptics.com/campaigns/cylinder-lens/
the equation is much easier for a single line generator. I am stuck at the point where I use a ...
- 1
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2
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429
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How do anti-reflection coatings in solar cells make light stay inside a solar cell?
We know that silicon is too shiny to absorb incoming light that's why anti-reflection coating is needed to make the incoming light stay inside the cell.
However, the problem is, even though the cell ...
1
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1
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159
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Birefringence in uniaxial materials
In linear optics, when treating anisotropic uniaxial materials we get the frensel equation
this equation gives us two solution for n. My problem is that according to Snell's law, if I have two ...
- 1,774
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1
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3k
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Obtaining both relative permittivity and permeability from refractive index
The complex refractive index $\tilde{n}$ is related to the relative electric permittivity and the magnetic permeability with the relation
\begin{equation}
\tilde{n} = n + \mathrm{i} k= \sqrt{\...
- 2,302
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4
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224
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How can the speed of light in matter be measured?
Experiments such as Focault's measure speed of light in matter. Focault's experimental set-up is based on the idea that it takes more time for light to travel through matter, which will result in the ...
- 1,171
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0
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434
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Does reflection depend on wavelength?
I'm aware of processes like Rayleigh scattering, Compton scattering and pair production. But as these processes treat light as being particles(?) I'm not sure whether they are helpful to understand ...
- 1,537
2
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1
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154
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How to control the refractive index of semiconductors?
I keep seeing/hearing that the refractive index can be controlled in semiconductors, but every time I read something like that it's always something very specific, like "Refractive index ...
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1
answer
349
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Regarding measurements on traveling microscope
In a experiment with traveling microscope to determine thickness of a glass slab , what is the physical significance of the readings that we get from the vertical scale ?, Means What are two points ...
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0
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52
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Transparency of oil paints with the passage of time
I know that oil paints become transparent after the passage of time (as in the case of many of the Old Masters), because air oxidizes oil, raising its refractive index, so that scattering of light ...
1
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1
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144
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Phase shifted Optical Fiber Bragg grating Response
As we know there is a narrow notch in the reflectance spectrum of a Phase shifted FBG. We have Bragg condition for reflected band of any uniform FBG. My question is that, does anyone know any relation ...
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