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Questions tagged [refraction]

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

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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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How To Calculate Wavefront Error of a Lens

The wavefront describes the Optical Path Difference (OPD) of an optical system. Typically the OPD has the unit of microns. The OPD is the difference of the Optical Path Length (OPL) of an arbitrary ...
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What is happening to a wave at a media boundary?

Say we have a light wave going from air to plastic, refractive indexes 1 and 1.5 respectively. What exactly is happening to the properties of the wave and why? Taking wavespeed as v, frequency as f, ...
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Mathematics supporting the classical explanation of why the phase speed of light slows down in a medium

Consider the answer here by Chad Orzel which explains how a monochromatic light can slow down in a medium. He explains, You can think each of the atoms (of the medium) as being like a little dipole,...
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What does it mean to say that glass has refractive index 1.5?

The refractive index of a material depends on the wavelength of the light incident upon it which is why dispersion happens. When we say that glass has refractive index 1.5 which wavelength do we have ...
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1answer
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Can light in a medium travel faster than speed of light $c$ in vacuum?

Refractive index of medium $m$, $n_m$, is given by $$n_m = \sqrt{\mu_r\epsilon_r}$$where $\mu_r$ and $\epsilon_r$ are permittivity and permeability of the medium respectively. And, velocity of light ...
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What is Cherenkov radiation? [duplicate]

What is Cherenkov radiation? I came across this concept when I was learning SR. Why can't particles moving at speed of excess of speed of light in the medium. Why it does not violate the limitation ...
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The Speed of Light and Its Medium's Density

When reviewing a refractive index chart there is a relationship to the density of the medium and the velocity of electromagnetic radiation through the medium. The lower the density the greater the ...
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Speed of electromagnetic wave [closed]

On dispersion, speed of wave is inversely proportional to its wavelength. Therefore, gamma has max.speed. But then in visible light, violet has least wavelength still it has least speed in visible ...
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2answers
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Does TIR obeys laws of reflection?

After reaching the critical angle, do Snell's laws and laws of reflection hold good?
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37 views

Amplitude of wave

Does amplitude of wave changes during refraction of wave If it will changes,why? I have been searched for internet but still cannot find a complete answer
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Image produced by unknown lens

Is it possible for an unknown lens to produce a real and magnified image on the side opposite the object? [Background] In a question I was given an unknown lens with a focal length of 20cm. The ...
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2answers
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light travels the fastest path of two points, how do you determine those two points?

so in this diagram from Richard Feynman's book: QED Strange Theory of Light and Mater the light takes the fastest path from S to P and the lens makes it so that there are many fastest paths that go ...
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1answer
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Reflection and transmission of EM waves

I'm reading "Introduction to Electrodynamics" by David J. Girffiths and the following assumption is confusing me: We have an EM wave inciding on a surface, Then, when applying the boundary ...
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1answer
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How much does temperature affect the time of sunrise?

Please forgive me if this is a dumb question, or if my understanding of basic physics is wrong. Please feel free to correct me. As I understand it, if the Earth didn't have any atmosphere, then the ...
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2answers
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Is snow falling too fast or too reflective to produce rainbow?

Imagine millions of water molecules suspending in the air starts to turn into snow, I like to know the exact reason why we cannot have snow bow, is it due to the speed of each snow falling very fast ...
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Why do lens (convex) not introduce any path difference to light incident on it?

My understanding is that the top rays spend less time inside the lens where the speed of light is slow and the middle rays spend more time inside the lens so the time is kind of compensated . But I'm ...
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Are rainbows three dimensional? If so, what determines their depth? [duplicate]

I am wondering whether rainbows are three dimensional, and if so, what determine their depth? How to calculate the depth of a rainbow, given its radius? From what I understand, all rainbows are ...
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Why does reflection occur on transparent materials? [duplicate]

Why does reflection occur on transparent materials? For example, air/glass or air/water (two different interfaces) Mostly it's refraction that's occurring, but I also see some reflection. Why is that?...
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1answer
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Refraction of matter waves

My question is a bit messy, so here is the background: Normally the trajectory of a massive particle in the presence of a gravitational field is described in the context of general relativity. ...
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2answers
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Reflectivity with Complex Refractive Index

I would like to ask a followup question on a previous post found here. Starting from the general expression for reflectivity: $$R = \bigl\lvert\frac{n_1-n_2}{n_1+n_2}\bigr\rvert^2$$ and substituting ...
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Evanescent wave in absorbing medium

Classic setup : Reflection and refraction with Snell-Descartes' law. Having 2 medium (1 and 2) with the normal n being oriented from 1 to 2 and placing ourselves in the incidence plane, we assume n ...
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1answer
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Feynman Lecture 33: Fresnel coefficients derivation

The Fresnel coefficients are: $ a=\frac{2\sin\,(r)\cos\,(i)}{\sin\,(i+r)},\quad b=-\frac{\sin\,(i-r)}{\sin\,(i+r)},\quad A=\frac{2\sin\,(r)\cos\,(i)}{\sin\,(i+r)\cos\,(i-r)},\quad B=-\frac{\tan\,(i-r)...
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1answer
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Feynman Lecture 33: Are Fresnel coefficients real?

In the Section 33-6 Feynman says: It is possible to go on with arguments of this nature and deduce that $b$ is real. To prove this, one must consider a case where light is coming from both ...
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How does refractive index increase in anomalous dispersion?

Refractive index generally increases with decrease in wavelength but in anomalous dispersion it decreases with decrease in wavelength. What causes it to be like that?
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2answers
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What really is the speed of light in a medium/vacuum, group or phase velocity?

While reading about refractive index 2 terms popped up, group velocity which alway slows down in a medium and phase velocity which may exceed speed of light. Say in a complete vacuum and using laser ...
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3answers
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Rule of addition of velocities in water

Is the speed of light still the same for all inertial observers in water? If not, what are the rules of addition of velocities in water according to special relativity?
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2answers
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Property of light in different media?

Shouldn't keeping a colored frame in front a flash light ( white light ) change its wavelength or frequency?But I have also learned that light doesn't change its frequency when going from one medium ...
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1answer
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Curved Light stream?

I was wondering, a while ago, i asked if there is a way to bend light someway, which I got the answer is index of refraction. In this question I wish to know if this mention when applied with a dense ...
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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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2answers
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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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1answer
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Relative Permittivity in a “Good Conductor”

I have a question in which I need to show that sea water is effectively a "good conductor", when considering the propagation of radio waves of frequency $< 10^9$. We're given that the conductivity ...
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1answer
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What causes these diamonds in water droplets on a screen?

It was raining yesterday and the screen of my iPad ended up covered in varying sized water droplets. As you can see, the smallest water droplets look transparent, and then as the size increases the ...
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2answers
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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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1answer
71 views

Why is the thin prism always in the position of minimum deviation? [closed]

Our textbook says that a thin prism (a prism of angle less than 10°) is always in the position of minimum deviation, but doesn't provide any explanation as to why that it is. What would happen if I ...
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0answers
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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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What is the speed of a photon in water?

What is the speed of light in water? The speed of light in vacuum, divided by the index of refraction for water. And what is the speed of a photon in water?
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1answer
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Value of complex angle in Snell's law

According to Snell's law: $$\sin \theta_t = \displaystyle \frac{n_1}{n_2} \sin \theta_i$$ where $\theta_i$ is the incidence angle in medium 1 and (after the ray crossed the interface between medium ...
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1answer
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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). ...
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2answers
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image formation by lenses

Why is the image formed by an object as described in the picture can be derived only from these three ray of lights?Every point on the object has multiple ray of lights going in every direction, how ...
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Confusion over Snell's law [duplicate]

Does the angle of refraction always have $n_2$ as its refractive index? As far as I know, $$\frac{\sin\theta_i}{\sin\theta_r} = \frac{n_2}{n_1}.$$ So I got this question here: Calculate the ...
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1answer
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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 ...
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1answer
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Is refraction a type of transmission?

I had read a passage somewhere stating that there are three possibilities when light falls on an object. It absorbs some of it, reflects some of it and transmits some (pass through). However, I did ...
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1answer
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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 ...
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1answer
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How does apparent depth depend on viewing angle?

In derivations of apparent depth and articles on refraction the approximation that the viewing angle is small is made in order to derive that $$D_a = \frac{n_v}{n_o} D_o,$$ where $D_a$ is the ...
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5answers
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Is there a medium less dense than vacuum, in which light can travel faster than $c$? [closed]

Is there a medium less dense than vacuum, in which light can travel faster than $c$? If not, can we make it?
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2answers
69 views

Huygens' principle

How do we know that the angle ADC is right angle here?
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1answer
99 views

Huygen's Principle, Snell's law and velocity of light

Can you deduce Snell's law from Huygen's Principle without knowing in which medium the velocity is going to less? Of all the derivations I have seen of Snell's law using Huygen's Principle (light ...
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1answer
66 views

Is there refraction upon frustrated total internal reflection?

If the incidence angle of a light ray on an interface is greater than the critical angle, but theres a third medium with a higher refractive index than the second, lower refractive medium ~ few ...