# 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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### Complete the concave ray diagram to show the path of the rays after refraction through the lens [closed]

Ray diagram, Path of the refracted rays
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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 ...
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### Diffraction when the wavefront is not parallel to the plane

I am studying Feynman's chapter on the origin of the index of the refractive index (see this link). If I am not mistaken, what he does is to prove that when a wave enters a medium (modelled as a ...
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### Snell's law in materials having negative permittivity only?

We have reverse Snell's law in negative index materials (having negative permittivity and permeability). If we have a material with only negative permittivity , then can we also have reverse Snell's ...
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### Most generic form of refractive index tensors

The refractive index of a material is in general a $3x3$ tensor (as in the case of birefringent crystals). From literature, it seems that in the case of transparent crystals, this tensor is in general ...
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### Relating Brachistochrone problem to Fermat's principle of least time [closed]

When I came across the Brachistochrone problem, my teacher said we could relate it to Fermat's principle of least time. So, we could make many glass slabs of high $\mathrm dx$, and every slab has a ...
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### Huygens' principle and the laws of reflection/refraction

As I understand the Huygens principle, all points on the wavefront are sources of secondary spherical wavelets and the tangent to these wavelets will form new wavefront. This is used to prove the ...
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### Is there a good quantum explanation of refraction? [duplicate]

I'm aware of the classical explanation of refraction which deals with light being a wave that gets "slowed" down while passing from a medium to another. One problem that I have with this ...
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### At which wavelengths do photons behave like X-ray?

Hard X-rays of wavelengths of about an angstrom are very different than regular lights in a way that they can’t be reflected or refracted, which means their refractive index is always close to 1 ...
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### What does the optical Hamiltonian mean?

So I was trying to demonstrate Snell's law with Hamilton's equations, and when I got the Hamiltonian: $$H = -\sqrt{n^2-p_{1}^2-p_{2}^2}.$$ I had a question about what this Hamiltonian indicates. I ...
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### Why can't we see green color in the sky? [duplicate]

From sunrise to sunset we can see a variety of colors in the sky. For example, during morning the most dominant color is blue whereas during sunset orange,red,yellow and there shades are more dominant....
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### Inconvenience of speed of light in optic fiber

As far as I'm concerned, optic fiber is great in order to transport information quickly using light. Since light needs to undergo total internal reflection every single time it hits the walls of the ...
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### How to Calculate Focal Length when in another medium?

How do you calculate the focal length of a lens when it is placed into another medium, if I only have the focal length of a lens in the air? I understand that the lensmaker's equation should be used, ...
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### What is a convex-concave lens?

I came across this term while studying for optics, and I'm unsure as to what this means. My thinking is that it might be a meniscus lens, but the text separately give two different models for each ...
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### I need to calculate the lateral displacement of light from a glass slab

I think I might have a solution to calculation the lateral displacement of light, however I'd like informed opinion on whether this is right. We first extend the incident line forwards. Now, we ...
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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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### How does Snell's law work with a complex refractive index?

In order to calculate Fresnel coefficients for layered media, we often need to calculate the angle that light travels inside a material with complex refractive index. Naturally, this is related to the ...
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### Behaviour of light in non-Newtonian fluids

So if a ray of light is passed through a cuboidal glass tub, and refraction occurs for the first time and if force is applied on the the fluid laterally, the viscosity would vary and so would it's ...
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### Why total reflection happens at only 1 angle?

The critical angle can be intuitively understood by Snell's law.If the incident medium has a bigger diffraction index than the refracted medium then according to Snell's law the refracted ray will be ...
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### How do parallel reflected rays meet to form image at infinity? If they never meet then how is image formed?

In my textbooks it is written that when an object is kept at focus, its image is formed at infinity and is real. But how is this possible because parallel lines never meet and it is necessary for rays ...
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### Ray separation in waveplates

In a birefringent medium, the ordinary and extraordinary rays have different Pointing-vector directions and, therefore, different propagation directions, since the direction of the Poyting-vector ...
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### Lens maker’s formula from parabolic approximation

I’m attempting to derive the lens maker’s formula for a thin or thick lens using the parabolic approximation. I’m familiar with the other proof using the law of refraction and different angles. The ...
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### Property of total internal reflection question

If I create a medium with gradually decreasing refractive index from once face at index 2.0 and other at 1.01, and show a beam of light upon the optically denser side, will there be any losses upon ...
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Problem: Figure shows two spherical surfaces of radii $R$ and $2R$ separating three transparent media of refractive indices $\mu_1=1, \mu_2=2$ and $\mu_3=4$. A ray of light travelling in medium $\... • 159 0 votes 0 answers 37 views ### Is the relativistic energy-momentum relation fundamental? [duplicate] The following relativistic energy-momentum relationship is taken to be fundamental: $$E^2=p^2c^2+m_0^2c^4.\tag{1}$$ Let us specialize to massless particles ($m_0=0$) so that we have: $$E=p\ c.\tag{2}$$... • 5,925 0 votes 2 answers 74 views ### Is there a way to calculate the angle between the refracted and reflected rays given the refractive index? Is there a way to calculate the refracted and reflected rays? I know we use Snell's law to calculate the refracted rays, but is there a formula to calculate the angle of the reflected rays, or does it ... • 187 7 votes 2 answers 1k views ### Fermat principle: how did they know the speed of light in different mediums? Pierre de Fermat derived his principle of least time by considering the path that light would take when traveling between two points. He postulated that light would follow the path that minimized the ... 3 votes 0 answers 60 views ### What causes the plane contrails to bend in the foreground of the eclipse? This looks almost like refractive index of air is different in the shadowed part, but what would cause that? • 5,329 2 votes 0 answers 35 views ### Apparent position of object in bowl of water Say you have a bowl of water and you keep an object in it. What would the apparent position of an object inside the bowl from the position of an outside observer? Will the curvature of the spherical ... • 187 5 votes 1 answer 407 views ### Difference between deviation of ray and wavefront This is a reference to the question posted by Govind Prajapat Refraction of light through a slab of variable refractive index A monochromatic light wave is incident normally on a glass slab of ... • 61 0 votes 2 answers 66 views ### Is refraction a special case of diffraction according to the book by Charles Kittel? Wikipedia defines diffraction as - Diffraction is the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/... 1 vote 0 answers 34 views ### QFT view of lower light speed of light in medium [duplicate] In classical EM theory, if we have a medium whose dielectric coefficient is independent of wavelengths (suppose we filter the incoming signal to a certain frequency band), then the waveform gets to ... 0 votes 0 answers 26 views ### Why the photons are deflected during the refraction? [duplicate] From what I learnt, when photons are passing throw a denser environnement with an positive angle (from the atmosphere to water for exemple), they are slow down. But I can't understand how this ... 0 votes 0 answers 42 views ### Why do shockwaves refract when they travel into the ground? If a shockwave from something like an explosion travels into the ground, why will it refract? The speed of sound is far different in the ground, but what would make it refract? I can’t seem to find ... • 275 1 vote 1 answer 43 views ### How are shockwaves able to refract? How are shockwaves able to refract? As said here, When two shock waves collide, they interact with each other and produce complex patterns of compression, rarefaction, and reflection. The resulting ... • 275 1 vote 4 answers 99 views ### Why does light bend through a different medium? How does light going through a medium make light refract? Here’s a good picture : The problem with this analogy is it depends on the students or light being connected to each other and as far as I ... • 275 2 votes 0 answers 27 views ### Definition of the displacement field in classical field Lagrangian In a BSM related paper (in appendix B), the authors use an effective Lagrangian$\mathcal{L}_{EFT}$, and define the following fields: $$\mathbf{D} = \frac{\partial\mathcal{L}_{EFT}}{\partial\mathbf{E}... • 143 2 votes 1 answer 113 views ### Why is the refractive index for light rays travelling in circular paths proportional to 1/r? While studying optics, I came across a problem with solution in which the trajectory of light rays was known—circular paths around a fixed point in space, and the question was that of determining the ... 1 vote 1 answer 89 views ### Why do highlights occur on edges? [closed] When looking at an object, the highlights are usually on the corners and edges. Highlights can occur anywhere on an object, but it seems like the brightest parts are where it is the most sharp. • 21 0 votes 1 answer 123 views ### Wave propagation in inhomogeneous media There is a problem I'm trying to solve for some time now and is about the standard (?) approximation that it is made when one tries to solve the Helmholtz equation in inhomogeneous media, that is \... 0 votes 0 answers 50 views ### Can anyone explain convergence of parallel rays on the focus of a parabolic reflector using Fermat's Principle? Can anyone explain convergence of parallel rays on the focus of a parabolic reflector using Fermat's Principle? using optimization techniques from calculus? 1 vote 0 answers 32 views ### Microscopic model of complex refractive index In my Electromagnetic Optics class, we tried to reconcile the microscopic (optical) properties of matter with its macroscopic counterparts, and one of the most challenging properties is the (complex) ... • 1,616 0 votes 0 answers 28 views ### How does an electromagnetic wave behave when it enters a medium with refractive index less than unity? From what I am able to find, the phase velosity of the wave exceeds c, but the group velosity remains less than c. However, why does the wave form wavepackets after entering a medium with refractive ... • 11 0 votes 0 answers 68 views ### Finding the limiting refractive index of a rainbow Give the limiting refractive index of a rainbow. The raindrops are modelled as spherical droplets, with refractive index n, with parallel rays from the Sun incident on it. I have a very limited ... 0 votes 1 answer 39 views ### Can anyone explain the relationship between the refractive index, the speed, wavelength and angle of a wave? Can anyone explain the relationship between the refractive index, the speed, wavelength and angle of a wave? in my book is states that$$n = \frac{v_1}{v_2} = \frac{\sin θ_1}{\sin θ_2} = \frac{λ_1}{... 3 votes 2 answers 134 views ### Why is$c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}\$?

I'm sorry if this is a duplicate but I didn't find my answer. I'm currently studying maxwell's equations and I know that by comparing the wave equation for either the magnetic or the electric field \...
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### Does light accelerate? [duplicate]

If considering the general formula for acceleration, ie. Δ V/ΔT, we would get zero as the velocity of light is constant and does not change. However, what about when photons travel through different ...
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### Minimum Radius of Curvature an Optical Fiber can be bent

Using the thickness and refractive index of an optical fiber, is it possible to know the maximum radius of curvature it can be bent before there are losses due to refraction? In my research, I came ...
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