# Questions tagged [refraction]

Change in the direction of propagation of a wave when its transmitting medium changes.

147 questions with no upvoted or accepted answers
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193 views

### Paint: “Darker When Dry”?

A great question I enjoy bringing up is why are things, in general, "darker when wet". This applies to porous and granular materials like wetted stone, paper, sand etc. It also comes up in painting ...
332 views

### Glasses underwater

So I figured the refraction of the cornea is based on the index of air and the vitrous humor to make a perfect image. Underwater this is messed with because water has the same index as the eye. Hence ...
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### What is the upper bound for the index of refraction of space?

It seems that gravitational waves and gamma waves travail at about the same speed, arriving within seconds of each other over distances in the ranges of $10^6$LY. Naively, I would assume this caps the ...
66 views

### Why is refractive index equals to speed of light upon phase velocity and not group velocity?

We have been using group velocity for most purposes as its the velocity with which the wave packet travels, they why do we use phase velocity for calculating refractive index.
133 views

### Complex part of second-order susceptibility in nonlinear optics

In optics, the absorption of photons by a material can be described by considering the material's susceptibility. For linear absorption (involving a single photon), we think about the imaginary part ...
464 views

### Under water light reflection of air in a cup vs water in a cup

The last time I was on vacation I was drinking on the swimming pool, and after I was finished with the drinks I started playing with the 2 plastic cups I had, and noticed that the air produces a ...
3k views

### What is Curvature of eye lens?

I wanted to know what do we mean by "curvature of eye lens", is it the reciprocal of $r$ i.e $c=1/r$ or is it synonymous to radius of curvature of the eye lens. Moreover how does aperture relate to ...
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### Can a powder be transparent?

I know that even glass powder is white due to refraction and internal reflection. So to be transparent, the index of refraction would need to be close to 1 (air). I also know that the index of ...
202 views

### Photons when passing through matter

I am wondering whether there is a simple—or complicated—way to explain from a purely quantum mechanics (or QFT) viewpoint what happens to the photons when they go through some material whose index of ...
283 views

### False sunset and false sunrise time estimation

False sunset and false sunrise are described . Here is a sample day rise and set time according to AccuWheather site and calculated value of sunrise and sunset in my country. Could you please help ...
119 views

### Mathematical approaches to atmospheric refraction

Understanding atmospheric refraction, particularly of ultraviolet, and into the blue part of the visible spectrum is of great interest to me. Although, I have a strong background in trigonometry and ...
64 views

### How do I use a sunstone? How does it work?

I have acquired two pieces of Icelandic Spar (optical calcite) with surface and internal fractures that should be serviceable as sunstones. I have observed the double refraction and cancelling double ...
78 views

### Can the Dirac Hamiltonian accommodate a variable speed of light?

The Dirac Hamiltonian has the form1 $$\left[\beta m c^2+c\sum_{n=1}^3\alpha_np_n\right]$$ where $\alpha_n$ and $\beta$ are Hermitian matrices, and $c$ is the speed of light. My question: Is there a ...
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### Light hitting a GRIN (Gradient-index) lens at the optical angle

In the image below, rays of light are hitting the GRIN (Gradient-index) lens at the optical angle and then converge towards the optical axis. Why do they do this? The refractive index is only a ...
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### How do we know that light cannot travel faster than it does?

We assume the speed of light in vacuum is its maximum speed but can we not assume that it could be faster, or slower?
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### Maximum intensification by refraction

Suppose that a beam of light in a medium with index of refraction $n$ reaches the surface of the medium, with vacuum on the outside. Its incident angle with respect to the normal is $\theta$. Only a ...
90 views

### Torque on Quarter-Wave Plate

When circularly polarized light is passed through a quarter-wave plate, the plate experiences a torque. I understand this is true because angular momentum must be conserved, but I don't understand ...
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### Integrating over Snell's law with a varying index of refraction

I am working on a research practical and I encountered the problem of having to integrate over Snell's law. The exact problem is that I have a varying index of refraction, which is a function of the ...
110 views

### When does refraction begin?

As a wave function (a single quantum of field excitation) enters a refractory medium, does it begin to refract only after the entire wavelength has entered or does the leading edge of the wavelength ...
245 views

### WHY do waves diffract - what is the mechanism behind the diffraction?

Having recently studied wave diffraction at an introductory level, I don't feel that I understand why waves diffract like they do. What is it about the obstacle or the waves interaction with it which ...
124 views

### Aquarium/refractive indices/detector

Quick question: I'm currently fiddling around with this homework of mine and I seem to be lacking some basic optics knowledge apparently. An aquarium is filled with a fluid as seen in the figure ...
70 views

### Odd order of colour fringes around cloud

The other day I took this photograph of a thundercloud that moved between myself and the sun. Around the edge of the cloud there were some coloured fringes that I first took to be a variant on a ...
669 views

### What happens when light is reflected from a surface moving in a medium with a huge refractive index?

Imagine a mirror is moving away from a light source in a substance through which the speed of light is very slow -- so slow that the speed of the mirror is close to being the same as the speed of the ...
241 views

### If a beam of light follows the path $y(x)=y_0\sin(x/y_0)$, what is the index of refraction?

An exam question that showed up while I was studying: A plane wave refracts and follows a ray given by the equation $y=y_0\sin(x/y_0)$ where $y_0$ is a constant. Find the refractive index $n(y)$ ...
736 views

### Nonlinear refraction index of vacuum above Schwinger limit

This question is more about trying to feel the waters in our current abilities to compute (or roughly estimate) the refraction index of vacuum, specifically when high numbers of electromagnetic quanta ...
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### Modeling a spray painted polyurethane surface reflection

I'm modeling light interaction/reflection from a fiberglass surface with polyurethane epoxy (that is very reflective) that has been spray painted with a matte black paint. I'm looking for some input -...
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### Changing the refractive index of biological tissue using Radio Frequency (RF)

I have been looking into changing the refractive index of a specific medium initially using Ultrasound in a known location via a mechanical Doppler shift of the emitter (Mahan et al., 1998) which has ...
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### Thickness and refractive index of silica gel layer between fused silica and water interface

I learned that when fused silica contact with water, a layer of silica gel will be formed. However, I cannot find any reference about the thickness and the refractive index of the silica gel. Can ...
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### Phase difference and optical path difference (OPD)

My textbook says that $\frac{\delta}{2\pi}=\frac{\Delta L}{\lambda}$, where $\delta$ is the phase difference and $\Delta L$ is so called path difference. But that's a cheat in my opinion. Even if the ...
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### Polishing Spherical Refracting surface vs Lens

My text book states that When we polish a spherical refracting surface (sphere) it doesn't behave as spherical surface and mirror .It still behaves as spherical surface. The polished side is just ...
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### Will the refractive index of a electrolyte change when chemical reaction happens?

Since polarization is the reason of refraction, then anything that changes the structure of molecule, atom, or electron will present as a change of reflection. Thus, to my understanding, chemical ...
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### Refractive index and optical fibre question

This is an A level AQA question: A signal is to be transmitted along an optical fibre of length 1200m. The signal consists of square pulses of white light and this is to be transmitted along the ...
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### How does temperature affect the refractive index of a vinegar?

I’m conducting an experiment on the relationship between temperature of vinegar and its refractive index.
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### Rainbow angle equals tropics inclination… a coincidence?

An observer from ISS can find a rainbow forming under certain conditions ( of internal reflection /refraction) in a cloud of water droplets at the equator. It may be regarded as equivalent to a ...
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### Refractive Index in Ionized Liquid from Micro Aspect

I learned about the refractive index of gases and dense materials, which is a function of the atom number per volume, wavelength of electromagnetic wave, etc. However, what is the refractive of ...
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### Refraction of light with destructive interference

The wavelength of light determines it's refraction in a prism. But, what if two beams of light destructively interfere as they pass through a small prism, so there is no apparent wave or wavelength ...
42 views

### Refraction on the edge of mediums

Say I have this setup : Here a light ray (in red) is incident on the point A in such a way that it is collinear with AB, and the indices of refraction are as mentioned in the figure. So my question ...
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### working to understand virtual images

I'm starting to understand how to use lenses a bit more, but I'm still pretty lost. I'm building a project that's extremely similar to this one with the implementation. I think my biggest challenge ...
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### Phase shift for reflection and transmission on absorptive medium with complex refractive index

I am trying to come with a hand-waving explanation as to why the reflection and transmission peaks of a metal-coated Fabry-Perot cavity are shifted in frequency (see the paper by Monzon & al). ...
51 views

### Focal Power of a Plane Interface

We know that when converging beam of rays are more converging after passing through an instrument, then we say it is of positive focal power. If angle of convergence doesn't change it is of zero focal ...
52 views

### Different index of refraction for different prism

I would like to just know more why different prisms have different index of refraction? From the point of view of atomic physics or something? I do not seek for full proof and derivation (which is ...
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### Relativistic equations are medium dependent?

Einstein proposed that light travels with a universal velocity from Maxwell's equations on electromagnetism. But light has different velocity in different mediums, so does this imply that the ...
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### If the velocity of light is different in different medium is it wavelength changes or frequency changes?

We know that the velocity of light is equal to the product of it's wavelength and frequency. And when light goes from vacuum to any other medium it's velocity changes depending the mediums refractive ...
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### Is refractive index a property of the material or the light ray?

Why does it vary for e-ray and o-ray in nicol prism?
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### what is the refraction index in the upper atmosphere(e.g Theromosphere)?

I've been searching for the refraction index in the upper atmosphere such as Stratosphere and Thermosphere but I can't find it, all that I've seen is all equation without any number that I can use it. ...
684 views

### How does the temperature of water affect its refractive index?

I am aware this question has been asked many a time but i have never found a answer which satisfied my exact requirements. I recently completed an experiment on how refractive index is affected by ...
65 views

### Biconvex lenses in 2 media

The question is what is the formula of the focal length of a biconvex thin lens if object medium is water and the image medium is air. I know that we have: 1/f = (n-1)*(1/R1 - 1/R2) , if the medium ...
150 views

### Change of refractive index using semiconductor

I was wondering, if it is possible to change the refractive index of a semiconductor using an electric field or current? I have heard about injecting charges to tune the refractive index. How/Why does ...