# Tagged Questions

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

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### Some perspective on two slits

I am not a physicist but i enjoyed the subject as a hobby and have my formal education in the field of computer science. If any of what follows is a big flaw in my understanding, I hope it will be ...
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70 views

### How does a photon 'know' when to reflect in case of refraction? [on hold]

In thin-film interference and in glass fibers refraction is involved. Depending on the angle of which a light ray enters the material it will be reflected or transmitted. The refraction depends on the ...
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### Finding the index of refraction [closed]

I'm given the angle of incidence which is 60 degrees and the angle of refraction 27 degrees. And two possible indexes of refraction for the second medium which are 1.923 or 2.417. How do I figure out ...
1answer
27 views

### How does infrared light behave through water?

I have a project involving the detection of the presence of water in a cylindrical transparent plastic container (diameter=25cm) And I cannot put any device inside, so I was thinking of using and IR ...
1answer
46 views

### Change in Speed of Light [duplicate]

Whenever light enters from air to glass its speed decreases but when it cross the glass and again come in air its speed increases. What is the reason behind this property? What is slowing it and what ...
4answers
2k views

### To what extent can speed of light be reduced? [duplicate]

Light slows down upon entering different transparent objects, and the ratio is taken as refractive index of the object. If light can be slowed down, then is there a limit up to which it can be slowed ...
2answers
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### Is optical path length (OPL) usually in units of length, or wavelength?

When I do calculations, I usually define optical path length (OPL) of a path as the integral of index $n$ along a path divided by the vacuum wavelength, so that I can get the phase easily. So for a ...
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### How to account for lower tropospheric horizontal refraction

With regards to the lowest 5kms of the troposphere, the International Standard Atmosphere models don't support a notion of a linear increase in air density along Horizontal axes. Yet, the path of ...
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### What is the relationship between atmospheric refraction and path curvature?

Light traveling in a "curved" trajectory suggests a linear increase of the refractive index over the entire distance (uninterrupted super-refraction). A lapse in the increase of the refractive index ...
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### How is horizontal atmospheric refraction explained?

I can understand vertical atmospheric refraction due to a gradual change in the refractive index of air. The distances measured in this model are often great. Sun moon planets etc.. now the question I ...
2answers
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### Why is it easier to get sunburnt in the water? [duplicate]

I went today to the swimming pool and I remembered that when I was younger my mom used to tell me to be careful because you get sunburnt much more easily in the water than in the ground. I never gave ...
0answers
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### Relation between gas flow and refractive index?

As we know, different gas flow produce different refractive index. Is there any equation to prove this statement?
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### Can refraction be thought of as a special type of reflection?

So, I know the difference between refraction and reflection but I've been wondering today if maybe refraction could be thought of as a special type of reflection with a very obtuse angle. Reflection ...
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### Refraction at parabolic surfaces

Why is it that we don't find discussion of refraction at parabolic surfaces while we find plenty of discussions of refraction at spherical, elliptic and hyperbolic surfaces? Could you please give ...
2answers
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### Why doesn't sunlight ALWAYS get split (into monochromatic) when going through the clouds?

It is my understanding that clouds are largely made up of water, which is known to split white light into its frequency components, and that's why we see rainbows sometimes. My question is, with ...
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### Proving that angle of incidence over angle of reflection is constant in Snell's Law

First let me state what I think I know: Snell's Law states that $\frac{sin(i)}{sin(r)} = \frac{v_1}{v_2}= \frac{\lambda_1}{\lambda_2}= \frac{n_2}{n_1}$ where i is the angle of incidense and r is the ...
0answers
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### Reversibility of Path of Light and refraction at i(c)

After reflection in the below diagram, what would happen: Will it pass all the way at the surface of separation? Will it be refracted back at the critical angle, if so at which point. It seems ...
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### What is the difference between reflection and total internal reflection (TIR)?

I look at what TIR is and then what reflection is - when the angle of incidence and the angle of election are the same. And TIR is when the angle of incidence is greater than the critical angle. TIR ...
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### Beam of light from glass to air

I am reviewing some concepts on light and came across a question that puzzled me. A beam of light is incident from a glass into air. The incident ray is 60 degrees to the normal. The question actually ...
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### Special Relativity and its relation to refractive index [duplicate]

As is known, light slows down (compared to vacuum) whenever it enters a medium. Also, Special Relativity effectively puts a limit on the max. speed of any body. So is it possible for a body (in a ...
1answer
68 views

### Calculating angle of min deviation of prism [closed]

Two rays incident with angle 40 and 60 on one face of equilateral triangular prism the angle of deviation are equal .find angle of minimum deviation?
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### Reflection and angle of refraction

Does the angle of refraction depend on the properties of the material if the angle of the incidence is the same for two different materials? Say I shed light on a surface with angle $\theta$ and ...
1answer
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### Refraction of light [duplicate]

In a prism, violet light undergoes more refraction than light of higher wavelength. Is there any explanation as to why light of higher frequencies refract more than light of lower frequencies?
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### 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 ...
2answers
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### Refraction of Sound Waves

When sound waves go from air to water what will happen to the wavelength and the angle of refraction? I used the approach that we apply to light waves and concluded the wavelength will decrease and ...
2answers
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### Refraction of light rays

My textbook says that the greater the refractive index of a medium, the lower the speed of a light ray passing through it. Seawater has a slightly larger refractive index than fresh water. Light ray ...
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### Breakdown of Snell [closed]

I have reason to believe the following: If we are using an accurately formed thin prism, with an apical angle of let's say 2 degrees, and direct a monochromatic source beam thru a slit onto the ...
2answers
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### How does change in medium affect object distance/image distance?

Say,we have a container filled with a liquid of refractive index $7/5$ upto a height up $H$. There exists a plane glass mirror at the bottom of the container. Now if a fish were placed at a height of ...
1answer
863 views

### How can my window not scramble the image of my yard?

How can an image pass through a window if the atoms in the glass randomly emit photons in any direction? I've read that glass is transparent because the atoms don't readily adsorb visible light, so it ...
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### Does the angle of incidence change the refractive index?

I've been told if you plot a graph using the sine of the angle of incidence and the sine of the angle of transmission it should follow a linear regression $y = ax + b$. However, if you use certain ...
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### Frequency dependence of electromagnetic reflection

I was surprised to see that the Fresnel equations for reflection depends on refractive index and angle of incidence, but they do not depend on frequency. Why is this case? Are they restricted to ...
1answer
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### Does curving only the inner surface of a diving mask prevent blurred images?

Diving masks often have lenses built into the glass for divers who do not have perfect vision. The lenses in a diving mask faceplate often only have a curved surfaces on the inside glass. Why is this ...
2answers
8k views

### Why do I see better under water using swimming goggles? [duplicate]

I am myopic (I don't really know if this is relevant or not) and I usually swim without contact lenses. My vision is clearly better underwater when I am using swimming goggles. I have tried to ...
2answers
268 views

### Is light getting another color when travelling through a prism?

When white light travels through a prism the speed of this light is slowed down. Now there is a relation between speed of light, frequency and wavelength. So when a red light of 700nm enters a prism ...
1answer
98 views

### Does this picture look wrong to anyone else? [closed]

There is a typo. One which obfuscates the main point and makes it difficult for anyone unfamiliar with the problem to deduce the answer.
3answers
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### Derivation of the group velocity

I know that the group velocity of a light pulse is defined as \begin{split}v_g&=v_p\left(1+\frac{\lambda}{n}\frac{dn}{d\lambda}\right)\\ &=\frac{c}{n}\left(1+\frac{\lambda}{n}\frac{dn}{d\...
1answer
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### Sphere, silver reflector, refraction questions

A sphere with its back silvered can act as a retroreflector. When a fine beam of light is directed to the sphere as shown, it is refracted at the front surface, and focused on the rear interior ...
1answer
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### Can something go faster than the speed of light in a medium? [duplicate]

Since some mediums have an index of refraction more than 1, light goes slower than in a vacuum. Does this mean it is possible for particles to go faster than the speed of light in these mediums? If so,...
1answer
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### Is Snell's law a product of Gravitational Time Dilation?

Due to the proximity of atomic structures in a solid liquid or gas, does the gravity of these atoms warp time enough to cause light to move slower from the perspective of an outside observer?
1answer
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### Why is glass green? [duplicate]

When I look at a glass block at an angle the edges appear green, but when I look at the edge sideways, so that is directly in front of my eyes it appears transparent. Why?
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### When exactly do we substitute $\epsilon_0 \rightarrow \epsilon$ and $\mu_o \rightarrow \mu$?

If everything is embedded into vacuum, why aren't Maxwells Equations always with $\mu_o$ and $\epsilon_o$? When exactly do we have to make the substitution $\epsilon_0 \rightarrow \epsilon$ and \$\...
2answers
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### Difference between scattering and refraction?

I while back I learnt that when light is incident on a dipole the dipole will scatter the light, and when it is incident on a material of a different refractive index then the light refracts. From the ...
1answer
949 views

### Why is everything not transparent? [duplicate]

There is a related question on this site here: Why glass is transparent? Which explains that glass is transparent because the atoms in glass have very large energy differences between energy levels ...