Questions tagged [refraction]

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

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70
votes
8answers
10k views

What really causes light/photons to appear slower in media?

I know that if we solve the Maxwell equation, we will end up with the phase velocity of light being related to the permeability and the permittivity of the material. But this is not what I'm ...
57
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4answers
23k views

What is the mechanism behind the slowdown of light/photons in a transparent medium?

So light travels slower in glass (for example) than in a vacuum. What causes light to slow down? Or: How does it slow down? If light passes through the medium, is it not essentially traveling in the "...
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4answers
20k views

Why do prisms work (why is refraction frequency dependent)?

It is well known that a prism can "split light" by separating different frequencies of light: Many sources state that the reason this happens is that the index of refraction is different for ...
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3answers
8k views

How are classical optics phenomena explained in QED (Snell's law)?

How is the following classical optics phenomenon explained in quantum electrodynamics? Reflection and Refraction Are they simply due to photons being absorbed and re-emitted? How do we get to Snell'...
45
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3answers
15k views

How does light speed up after coming out of a glass slab?

As I learned today in school, my teacher told me that when light enters a glass slab it slows down due to the change in density and it speeds up as it goes out of the glass slab. This causes a lateral ...
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6answers
11k views

Do photons have acceleration?

Photons travel at the fastest speed in our universe, the speed of light. Do photons have acceleration?
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11answers
78k views

What determines color — wavelength or frequency?

What determines the color of light -- is it the wavelength of the light or the frequency? (i.e. If you put light through a medium other than air, in order to keep its color the same, which one would ...
38
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3answers
245k views

Virtual vs Real image

I'm doing magnification and lens in class currently, and I really don't get why virtual and real images are called what they are. A virtual image occurs the object is less than the focal length of ...
32
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3answers
166k views

Why does wavelength change as light enters a different medium?

When light waves enter a medium of higher refractive index than the previous, why is it that: Its wavelength decreases? The frequency of it has to stay the same?
18
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4answers
3k views

Looking for the actual reason of refraction explained precisely without analogies

I'm a high school teacher trying to teach my students (15year olds) about refraction. I've seen a lot of good analogies to explain why the light changes direction, like the marching band analogy, that ...
48
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6answers
105k views

Why doesn't the frequency of light change during refraction?

When light passes from one medium to another its velocity and wavelength change. Why doesn't frequency change in this phenomenon?
6
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1answer
6k views

How does a one-sided glass work?

How does a one-sided glass work? If seen from the outer side, we can see through thinking it is transparent, while if seen from the inside, the glass acts as a mirror. How?
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2answers
2k views

What happens if light/particles exceeded the speed of light for a particular medium

While the speed of light in vacuum is a universal constant ($c$), the speed at which light propagates in other materials/mediums may be less than $c$. This is obviously suggested by the fact that ...
4
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2answers
2k views

Why one should follow Snell's law for shortest time?

whenever two media and two velocities are involved, one must follow Snell's law if one wants to take the shortest time. Why snells law must be followed to travel diffrent media in shortest time? ...
12
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3answers
711 views

Optics: Derivation of $\vec\nabla{n} = \frac{d(n\hat{u})}{ds}$

I have been given this formula from optics here, with no background: $$\vec\nabla{n} = \frac{d(n\hat{u})}{ds}$$ Where $n$ is the refractive index and $\hat{u}$ is a unit vector tangent to the path $...
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5answers
148k views

Why does the road look like it's wet on hot days?

Often, I'll be driving down the road on a summer day, and as I look ahead toward the horizon, I notice that the road looks like there's a puddle of water on it, or that it was somehow wet. Of course, ...
9
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1answer
640 views

If refraction slows down light, isn't it possible to hold light still?

I have a quick question about the refraction of light, and I'm sorry if it seems a bit simplistic or even stupid, but I'm still learning. We know that when light passes through a denser medium, it ...
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6answers
6k views

Is it possible to witness a circular rainbow?

What conditions would make it possible to see a naturally occurring fully 360° circular rainbow? Would it even be possible?
22
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1answer
22k views

How does a photon travel through glass?

This was discussed in an answer to a related question but I think that it deserves a separate and, hopefully, more clear answer. Consider a single photon ($\lambda$=532 nm) traveling through a plate ...
16
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1answer
2k views

Why is not everything 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 ...
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2answers
10k views

Analytic solution for angle of minimum deviation? [closed]

Consider a simple prism with a prism angle $A$, angle of incidence $\theta_1$, angle of emergence $\theta_4$ and the first and second angle of refraction as $\theta_2,\theta_3$. the refractive index ...
43
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5answers
9k views

If a lens focuses all incoming light to a point, how do we get 2D images?

How do lenses produce 2-dimensional images, if a lens bends all incoming rays of light to intersect at the focal point? Shouldn't this produce a single dot of light on a screen placed at the focal ...
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3answers
33k views

Why would an object appear a different size when in water?

A friend of mine has a homework question and we're having some trouble figuring out what physical mechanisms come into play for this. An underwater swimmer sees a spherical air bubble that appears ...
10
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3answers
5k views

Does light change color on its way through a window? [duplicate]

Looking at the refractive index of glass, it's around $1.6$. Then the speed of light $x$ through light should be given by $$ 1.6 = \frac{3.0\times10^8}{x}, $$ so $x$ is about $2\times10^8~\mathrm{m}~\...
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4answers
127k views

Why do diamonds shine?

I have always wondered why diamonds shine. Can anyone tell me why?
26
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5answers
14k views

Eyes open under water

Yesterday I looked underwater with my eyes open (and no goggles) and I realized I can't see anything clearly. Everything looks very, very blurry. My guess is that the eye needs direct contact with air ...
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3answers
14k views

Why does light bend towards the normal when passing from a rarer to a denser medium?

Whenever light rays are entering a denser medium they bend towards the normal. Why do rays choose the path towards the normal? Why cannot they choose the path away form the normal?
2
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2answers
389 views

Density gradient in a shock wave of Supersonic Aircraft?

Shock waves are basically density gradients. Is the change in density continuous or discrete? By discrete I mean something Because it is a density gradient it must have refractive properties. Does ...
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3answers
4k views

Photon energy - momentum in matter

$E = h\nu$ and $P = h\nu/c$ in vacuum. If a photon enters water, it's frequency $\nu$ doesn't change. What are its energy and momentum : $h\nu$ ? and $h\nu/c$ ? Since part of it's energy and momentum ...
14
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3answers
7k views

Is true black possible?

Black is the absence of light because it absorbs light, but when we create black paint or black objects, light is always reflected, either in all directions in matte or smoothly in shiny black objects,...
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7answers
12k views

Why can we only “see” reflected light? [duplicate]

This is a question thats been bothering me a while. I don't even know if it makes sense or not (like if it is a physics question or becoming a philosophical one). But here it goes. The crux of my ...
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2answers
302 views

Why does electromagnetic refraction happen?

Why does refraction happen? In high school textbooks, it is stated that it happens because the speed that electromagnetic waves propagate in the media change. But why cant they continue propagating in ...
4
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2answers
744 views

Why is rainbow always circular?

From the article that I read on physics classroom website on rainbow, rainbow is formed with red on the top and violet on the bottom because violet refracts more, and has a smaller angle of deviation ...
2
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1answer
599 views

How are neutron refractive indices calculated?

I have been informed of the fact that neutrons refract similarly to light in accordance to Snell's Law. How would one calculate the refraction index for a neutron?
2
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1answer
607 views

Diffraction by blazed grating via reflection: why is the reflection angle diffrent depending on $\lambda$?

Consider a blazed grating as the one in picture. It is possible to obtain a diffraction of a beam of light as in a trasmission grating (diffraction of reflection grating) and different wavelenghts ...
2
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3answers
926 views

What makes a rainbow happen?

A rainbow is formed when a raindrop refracts light, but why then does the whole sky not become a huge rainbow when it rains? Would the light not be dispersed into ordinary white light? What causes it ...
2
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3answers
553 views

How Does $\epsilon$ Relate to the Dampened Harmonic Motion of Electrons?

I realize that the permittivity $\epsilon$ of a substance is easily calculated based on diffraction angles, but I am not satisfied with merely measuring it experimentally. I wish to understand its ...
7
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2answers
560 views

Rainbow Blackhole?

Can white light be broken into its component colors when gravitationally shifted by a black hole, in a manner similar to what a prism does? http://www.physics.utah.edu/~bromley/blackhole/index.html
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2answers
3k views

Refraction of light and frequency dependence

Why do higher frequency waves refract more, both ocean waves and light waves? Also why is energy stored in the frequency as opposed to the wavelength.
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2answers
7k views

Is there a theoretical maximum for refractive index?

May there be materials yet to be discovered which may have a higher refractive index than today's known materials (for wavelengths within the visible range)? Is there a theoretical limit for the ...
8
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3answers
5k views

How can a particle in a medium ever travel faster than light? [duplicate]

In some media, mass-carrying particles can go faster than light: Cherenkov radiation, ... is electromagnetic radiation emitted when a charged particle... passes through a dielectric medium at a ...
6
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2answers
2k views

why does the graph of deviation angle in a prism doesn't get a symmetry?

According to (i1+i2)-A , the graph of i1- and the angle of deviation shows below. This graph is not symmetrical. It usually oriented to right. According to above equation I can generally ...
4
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2answers
5k views

Wavelength-dependent refractive index

I read in a book about optical fibers that the different spectral components of a light pulse transmitted in the fiber propagate with different velocities due to a wavelength dependent refractive ...
3
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4answers
20k views

Why does a ray passing through optical centre remain undeviated?

How can it be explained using the laws of refraction that a light through optical centre of a lens passes undeviated? If we assume the portion of the lens in the middle to be made of even number of ...
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1answer
3k views

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?
3
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4answers
12k views

Relation between intensity of light and refractive index

The intensity of light (as calculated from time average of the poynting vector) is given by $I = (1/2) \epsilon v E_0^2$. Here the intensity is dependent on the velocity of light in the medium. The ...
2
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2answers
1k views

Imaginary number for extinction coefficient in complex refractive index

In complex refractive index on a material, $n=n'+ ik$, the imaginary part $k$ is physical meaning, as it shows absorption in the material but it is an imaginary. How we measure an imaginary values in ...
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vote
1answer
882 views

Determining the path of a light ray

Let's consider a ray in the plane $xy$. Let the refractive index be defined in any point of the plane with the function $n(x,y)$. In time $t=0$ the ray is located in coordinates $(x_0, y_0)$ and its ...
9
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2answers
12k views

Purple doesn't occur in rainbow - or does it?

Usually, when asked whether the purple color exists rainbows, an answer similar to this is given: The purple color is perceived by human eyes via the activation of both red-sensitive and blue-...
4
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1answer
8k views

why does the optical media have different refractive indices?

Optical density is a measure of the refracting power of a medium. In other words, the higher the optical density, the more the light will be refracted or slowed down as it moves through the medium. ...