# Questions tagged [refraction]

Change in the direction of propagation of a wave when its transmitting medium changes. The tag does also apply to index of refraction.

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### Photon energy-momentum relation inside a material [duplicate]

I understand that the speed of light in a medium like glass, $c_n$, is reduced by the refractive index $n$ so that we have: $$c_n=\frac{c}{n},$$ where $c$ is the speed of light in the vacuum. Is it ...
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### Change of speed of light in case of normal incidence

According to Snell's Law: $n_1\sin θ_1~=~n_2\sin \theta_2.$ If, $\theta_1 = \theta_2 =~0$ there is no bending but the speed of light changes according to the refractive index. Is this the case or I am ...
1 vote
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### Determining the location of light receivers using signals propagating in anisotropic media

Problem. I have a set of $16$ light receivers with entirely unknown locations, and a pair of light transmitters with exactly known locations. One light transmitter is stationary, and located near to ...
1 vote
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### Why is the time taken for light propagation between two points in anisotropic media independent of $y$?

Background Light propagating in an anisotropic medium does not (in general) take a straight-line path between two points. The propagation time between those points, then, is dependent on the total ...
1 vote
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### Speed of EM Waves

We know that for electromagnetic waves, according to Maxwell's Theory $$v=\frac{1}{\sqrt{\mu\epsilon}}$$ Now consider an opaque object like say Gold. It has a particular value of permittivity and ...
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### Why double rainbows have the orders of the color bands in them inverted?

I did some online search and found the explanation using the following two diagrams. It's not perfectly convincing to me. Or at least it is not clear to me in the following details of the process: ...
227 views

### Can we trap a light ray in a prism (in geometric optics)?

In geometric optics, light rays can enter a (finite) prism of constant refractive index, and bounce off the edges as long as the incident angle is less than the critical angle of the medium. Is there ...
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### Is there a maximum angle for total internal reflection (TIR) above which TIR won't happen? [closed]

I came across such a concept when I learnt about fibre optic cables and T.I.R. There was this question: Light guidance in an optical fibre can be understood by considering a structure comprising of ...
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### Focus sunlight into a line and not just a point with lenses

Using a magnifying lens with the sun as the source, one can focus the light in a single point. Is it possible to use just lenses, or any number of transparent materials of any particular shapes, to ...
45 views

### Is it possible to have single-sided refraction?

Is it possible to have light refract in one direction, then reflect off a mirror but come back as a straight line like the picture below? The context of this problem is in lens optics when a ...
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### Does the intensity of blackbody radiation depend on the speed of light in the medium?

In 1863, in “ON THE CONCENTRATION OF RAYS OF HEAT AND LIGHT, AND ON THE LIMITS OF ITS ACTION”, Clausius wrote in the conclusion: To harmonize the effects of ordinary radiation, without concentration, ...
1 vote
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### Is $n=\sqrt{\mu_r\varepsilon_r}$ always true? even with complex value?

I have trouble deriving a supposedly "well-known" equation used in condensed matter physics: $$n^2=\mu_r\varepsilon_r+\frac{i\mu_r\sigma}{\varepsilon_r\omega}$$ I'm sure that $n$ and $\sigma$...
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### Do these two separate light pulses (in sequence) interfere in this scenario? Why or why not?

This question is inspired by the recent "double-slit experiment in time" experiment that was popularized. See here and here. I have not looked into the original paper in detail, so my ...
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### How to derive Fresnel's tangent law?

In this Wikipedia post the $r_p$ Fresnel reflection coefficient is given by: $$r_p = \frac{\tan{(\theta_i - \theta_t)}}{\tan{(\theta_i + \theta_t)}}.$$ How can this be derived from the previous ...
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### Can a mote of dust create a rainbow/prism like effect if floating inside the light of a sunbeam and seen from the right angle and/or device?

The device could be a telescope, microscope, camera, or anything that zooms in with great clarity. I'm pretty sure that lots of dust together in one place in a sunbeam can have this effect (please ...
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### Refraction of light vs. electrostatic electric field lines [closed]

As we all know light being an EMR has a magnetic and electric field component perpendicular to it. Also when light changes it's medium it gets deviated. But in electrostatics when we consider electric ...
1 vote
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### Change in nature of image: Putting a concave mirror in water vs in air

I was wondering if we put a concave mirror in water, what will be the difference in the image formed by it in air vs water? Exception: Here I mean except when rays come from infinity (e.g., sun) ...
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### Light Refraction, Biconcave Lense, Creating Rough Diagram to Explain to Child

I've read that the refraction of light at the boundary of a medium can be described as follows: -a line of connected people marching. one side of the line enters mud, and slows down. This causes the ...
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### Do any of the color bands in a rainbow contain an electrical charge relative to clouds that might explain a photo of lightning striking a rainbow?

Caveat: While I am not a physicist myself, I am extremely interested in physical phenomena. I am well versed in electrical theory, and I am aware of the attraction between the bottoms of clouds and ...
1 vote
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### How does Dipole coupling affect macroscopic polarizability and refractive index

I have taken some measurements of refractive index (refractometer (commercial Brix meter), nD20 i.e. 20 degrees C and 589 nm) and density of sucrose/water mixtures and also of ethanol/water mixtures. ...
1 vote
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### What causes the distortion of an image when seen through a water droplet?

I'm trying to explain what causes an image to be distorted when seen through a water droplet. Specifically, my example is that of a drop of water on a car window. We can see that the image is reversed,...
1 vote
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### Deriving the focal length of a graded index lens (GRIN)

I want to find a closed expression of the focal length of a graded index since I don't manage to find any on the internet. I already checked this out: Determining the focal length of a gradient index ...
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### Wave-packet in configuration space and deriving Schrodinger equation with this approach

In the book "Group theory and it's Applications to the Quantum Mechanics of atomic spectra " by Eugene P. Wigner in chapter 4 The elements of quantum mechanics it is written Consider a many ...
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### Fermat's principle and a non-physical conclusion

Fermat's Principle is the statement that a ray will follow a minimum-time path between a point, A, to a point, B. So, if I have a block of material of high refractive index, so that it slows the light ...
1 vote
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### What are the physics behinde reflection and refraction of electromagnetic wave at a dialectric surface?

I have understood the most of the equations that lead to the Fresnel-Equations from electromagnetic waves and Maxwell equations. But not enough to understand what is happening. So I don't ask for an ...
1 vote
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### Ambiguity in proof of angle of minimum deviation of for a prism [closed]

I have stumbled upon a proof from one of my friends that for a prism, the angle of minimum deviation is that in which incident angle is equal to emergent angle. i.e. $$\delta = i + e - A$$ where $A$ = ...
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### Light in glass/water

When light enters water, the light changes their direction because they only use 75% of their speed in water, because the interactions with the electrons, the wavelength of the photon changes. We SEE ...
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### Refraction of light as seen from a glass of water

When we put a straw in a glass of water the size and bending is more when viewd from side than from up. Is this due to the effect of the glass?
1 vote
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### The light behavior from vacuum to glass [duplicate]

What does the statement labelled mean? This is in Feynman's lectures on physics. Why should the frequency in both vacuum and glass be same? What is the meaning, that charge sitting on the boundary ...
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### Would everything we see be delayed if light slowed down to 1ms?

I don't know much about physics, though it certainly interests me. so I apologize if this is a dumb question, but if we somehow slowed down the speed of light around us. (like we somehow made air have ...
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### Is there any physical explanation for negative extinction coefficient, $k(E)$, over a spectral range of energies?

Measured data for $n(E)$ of air were fitted to equations for $n(E)$ and $k(E)$. The measured data for n(E) spanned 0.734 to 6.702 eV. To obtain fits to the equations for n(E) and k(E) in the absence ...
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### Can prism separate different colour of light?

Can prism separate colours of light? For example, I have a purple colour. purple colour is by mixing of red and blue. I that possible when purple colour light is passed through a prism it separate the ...
1 vote
40 views

### Refractive index of air for different wavelangthes

When I tried to search about the refractive index of air, I found 1.00029. This is for which wavelength? How can I find refractive index of it for different wavelengthes like red light's wavelength ot ...
1 vote
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### Relationship between complex refractive index and complex conductivity in condensed matter physics

In my field (time-resolved spectroscopes of semiconductors), people use this equation like it was trivial and never cited a source or provide derivation: \tilde\sigma = i\omega\varepsilon_0 (1-\...
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### Is it possible to see real images without a screen?

I have always wondered about this question, so searched it up on the internet and there were contrasting ideas.Some said that it can be seen but the others said it can't. According to me we are able ...
1 vote
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### Is Huygens principle applicable in different mediums?

In the proof of refraction using Huygens principle, once the light hits different medium, it is said the position of light after 't' seconds in 'A' medium and 'B' medium should be on a straight line ...
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### Is there such a thing as a bare polariton?

When dealing with photons in matter, I have seen it treated in many ways depending on the material, this leads to exciton polaritons (when dealing with electrons and holes), plasmaritons (dealing with ...
131 views

### Do quasiphotons have mass?

If I understand correctly, per special relativity, anything that travels at a speed of $c$ must be massless and conversely, anything massless must travel at precisely $c$ in akl reference frame. We ...
287 views

### What's at the end of a rainbow?

I recently saw a video where someone saw the end of a rainbow as it went into a lake. How is this even possible considering the fact that rainbows have no ends and are circular in nature? Edit: I ...
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### Optics question: Simple way to transform a parallel bundle of collimated beamlets into a converging (diverging) bundle of collimated beamlets?

I'm searching for an optical element that converts a parallel bundle of individually collimated beamlets into a converging or diverging bundle of still collimated beamlets (or vice versa). So ...
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### Refraction of a Ray of Light [duplicate]

Why can no medium have a refractive index less than 1? Explain with Snell's Laws of Refraction of Light.
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### Why does a light wave travel at a different speed when the density of medium is different [duplicate]

Why does light waves travel at different speeds when the density of medium changes? Can you slow down light?
1 vote
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### Does using thinner glasses have any effect on how the eye look?

My daughter asked me to buy thin glasses for her eyes. So the power of the lenses are the same, but the glasses are thinner because the glasses use plastic with higher refraction index. Latter I found ...
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### Can a ray of light deviate passing from a rarer to a denser medium deviate beyond the normal?

Is this allowed? Technically, if the difference in the refractive indexes is big enough, and the ray of light has a low wavelength (violet), it should be able to deviate beyond the normal.
1 vote
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### Decoherence of a laser beam via oil emulsion

This is sort of a followup to an earlier question that I posted regarding how to destroy the temporal and/or spatial coherence of a laser beam. It was suggested to me that I could use a rapidly ...
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### Why are $\rm ZnSe$ beam-combiners typically "optimized" for a 45º angle of incidence?

Everywhere I look it seems that $\rm ZnSe$ beam combiners (as the ones sometimes used in $\rm CO_2$ [10600nm IR] laser cutters) are "optimized" or designed to work at a 45º angle of ...
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### Strength of electric field needed to observe noticeable effects on refraction in water

I was looking into the mechanism behind refraction and stumbled upon a Fermilab video explaining it has to do with the electric fields of the particles in the medium interacting interacting with the ...
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### Is it possible to measure the temperature of a candle by the diffraction method?

I am reading a book " Physics, Fun and Beyond" by Eduardo de Campos Valadares. In his book, he is mentioning about an experiment "bending laser beams with hot air." I am posting a ...