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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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43 views

### What determines the property of vacuum that allows EM field to propagate?

As in case of sound it the disturbance that propagates by exchange of energy between particles. what is analogously related to em wave, where there is propagation of energy stored in electric and ...
274 views

### Is the reason the sunshine is 'extra bright' after rain due to refraction of the additional water in the air?

Quite frequently after the sun comes out after rain I experience a 30 minute period where the sunshine is 'unusually bright'. Such that it makes my eyes water. My question is: Is the reason the ...
45 views

### Is refractive index a property of the material or the light ray?

Why does it vary for e-ray and o-ray in nicol prism?
252 views

### In refraction how does light interact with electrons if it is not absorbed? [duplicate]

What I (think I) understand: When light is refracted in a medium (say glass), the light interacts with the electrons in the medium and the electrons create new waves. Summing the waves with the ...
44 views

### Why do our eyes perceive changes in apparent position of stars as twinkling?

Okay, so we all know that the changes in refractive index leads to continuous changes in star's apparent position but then why don't we see them moving up and down rather than brighten and dim in ...
94 views

### Contradiction on the behavior of refractive index

The refractive index is given by: $$n = \sqrt{\mu_r \epsilon_r}$$ This equation is symmetric about wavelength and is same for all wavelength of light i.e. since $\mu_r$ and $\epsilon_r$ are ...
12k views

### What's the physics behind XKCD #2027 (time between lightning flash and radio wave burst)?

XKCD usually has solid (and often contemporary) science behind it. Lightning Difference, #2027 one says: Q: What’s that trick for telling how many miles away lightning is? A: Just count the ...
662 views

### resulting refractive index of multiple layers with different indexes

I am wondering whether my chain of thought is right because this seems very counterintuitive to me. But I calculated that if I have multiple layers with different refractive indexes stacked onto ...
67 views

### what is the refraction index in the upper atmosphere(e.g Theromosphere)?

I've been searching for the refraction index in the upper atmosphere such as Stratosphere and Thermosphere but I can't find it, all that I've seen is all equation without any number that I can use it. ...
152 views

### Does the optical density of a medium depend upon its mass density?

The optical density of a medium is quantified by its refractive index $n$. Does it have any correlation with the mass/number density of the medium? In other words is an optically denser medium must ...
146 views

### Can you burn invisible jelly balls with a laser?

Suppose you have some jelly balls with similar refractive index as that of water, like in this video. You put them in water, making it invisible. So, the optical behavior of the balls should be ...
113 views

### What refractive index should be used while calculating the focal length of lens using lensmaker's formula?

Suppose a lens is half dipped in liquid. Then should the refractive index of liquid with respect to air should be taken. Or should refractive index of glass wih respect to liquid be taken. Or perhaps ...
92 views

### What happens to a light ray after it enters a perfect sphere? [duplicate]

I am assuming a sphere which can reflect, refract and diffuse a light ray. So when a light ray hits the surface of the sphere from outside, a part of it gets reflected, a part of it gets diffused and ...
38 views

### When given light colour and refractive index, how do I find wavelength?

Example situation If I knew that this green light, which has a wavelength of 500 nm in air, travels through a medium with a refractive index of 2.4, how would I find the wavelength in the medium? ...
660 views

### What is bent light speed?

I have a question, if there is a straight beam of light that moves at the speed of light, is there a way to calculate the speed of bent light? since bending light causes it to lose momentum? Example, ...
60 views

### Why the purple and red light entering the prism is broken at different angles? [duplicate]

Lights entering the prism with different wavelengths at the same angle. why go to different directions? what happens step to step between the protons&electrons in glass and the photons? what is ...
40 views

### Change in color

We have studied that when light changes medium, its speed along with wavelength, changes. Does that means that if we are inside a pool of water and a red flash light is pointed towards us, it will ...
159 views

### Acceleration of photon

When light moves from one medium to another its speed changes due to the refractive index of the medium and so does its momentum given by $h/λ$. What is the acceleration of photon when it makes ...
3k views

### Why a light ray does not refract when it is incident normally to the surface?

I had read that when light enters a glass( or any other medium) its speed changes which lead to the bending of its path. But why doesn't light bend when it is incident normal to the surface. It is ...
1k views

### Weird Reflection Pattern in Reading Glasses

While fidgeting with a pair of reading glasses, I noticed a strange reflection pattern (shown in video and photo). I would appreciate it if anyone that knows more about this could help me figure out ...
799 views

### How does the temperature of water affect its refractive index?

I am aware this question has been asked many a time but i have never found a answer which satisfied my exact requirements. I recently completed an experiment on how refractive index is affected by ...
97 views

### What is light’s behavior in a medium?

I’ve been reading questions and answers to this topic and have conducted a few experiments as well to try and understand what happens to light in a medium. Somethings just don’t seem to make sense to ...
38 views

### Geometric optics limit in lens design [closed]

What is the rule-of-a-thumb ratio of lens' thickness to wavelength at which they can be designed using ray optics approximation? (The thickness is more relevant to gradient index lens, homogeneous ...
90 views

### Light double slit experiment

Does the light double slit experiment work equally regardless of it being done in a vacuum or a medium (gas or liquid)?
1k views

### How does the Huygens–Fresnel principle apply to diffraction?

I'm currently trying to understand the mechanics behind diffraction and gain a better understanding of the Huygens–Fresnel principle, but I've reached a hurdle that is making me question my ...
791 views

### Can relative permittivity be less than 1?

Relative permittivity shows that force of interaction in some media is 3 times less than in vacuum ($\varepsilon = 3$) for example. When looking tables of permittivity I never saw a value less than 1. ...
47 views

### What makes an object mirror? [duplicate]

All objects reflect some of the colours and then our eyes are able to see object of different colours. But when we see mirage in a desert then it seems that the sand of the desert is acting as a ...
99 views

### Why certain objects reflect while some refract?

Both reflection and refraction are processes where absorption and re-emission of electromagnetic waves occur, but they differ in the direction of re-emission. What factor particularly decides the ...
129 views

### if light source is bigger than the object, it is possible that shadow of the object is bigger than the object?

When sun light falls on my bathe tub i noticed that the shadow of any small particle floating on the water surface is bigger than the particle and also it is quite circular i.e. Deform from It's ...
70 views

### Biconvex lenses in 2 media

The question is what is the formula of the focal length of a biconvex thin lens if object medium is water and the image medium is air. I know that we have: 1/f = (n-1)*(1/R1 - 1/R2) , if the medium ...
3k 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 ...
156 views

### Change of refractive index using semiconductor

I was wondering, if it is possible to change the refractive index of a semiconductor using an electric field or current? I have heard about injecting charges to tune the refractive index. How/Why does ...
245 views

### What do individual rainbow-forming droplets look like?

Suppose we took a photo of a rainbow, but in such a huge resolution and sharp focus as to be able to see each droplet in good detail. What would the droplets look like? Would they be nearly uniformly ...
348 views

### Density and refractive index of Water/sugar solution

I can't find a correlation or equation for refractive index of water and sugar solution of known density. Do you know where to find it?
72 views

### Can we see through the central obstruction of a lens?

I have a very basic question in optics inspired by this article from the University of Stanford which clearly states that one should see a light source through a mask in the middle of a lens if the ...
4k views

### Can air make shadows?

I have read about schlieren photography which uses the ability of non-uniform air to create shadows. Is it really possible that air makes shadows?
107 views

### Why colorless gem having refractive index close to that of water becomes invisible in water?

Why does a glass rod or colorless gem having refractive index close to that of water becomes invisible in water? I couldn't get what happen that they tend to camouflage? Why can't our eye ...
66 views

### What wavelength of light has the greatest rate of reflection off of ice?

We are using a camera that is nearly flush against frosted ice (not perfectly clear, but pretty close). We are currently using white LED's, but very little of the light gets reflected back into the ...
156 views

### Surface that refracts all rays onto a single point

I am trying to find the equation to the interface separating two optically different medium which will focus all rays coming from a point B(b,0) in medium 2 ($\mu$=m) to a single point A(a,0) in ...
34 views

### Photon explanation of dielectric effects?

When an electromagnetic wave passes through a medium, the electric component of the wave will induce a dipole. I believe this can happen in a number of different ways, including rotating of a polar ...
1k views

### Deriving the law of reflection for a moving mirror in relativity

I am following a training course and came across this proof, from my colleague, that the ordinary law of reflection $\theta_i = \theta_r$ does not hold in relativity: Let $S$ be a perfectly ...
71 views

### Why is refractive index equals to speed of light upon phase velocity and not group velocity?

We have been using group velocity for most purposes as its the velocity with which the wave packet travels, they why do we use phase velocity for calculating refractive index.
93 views

### What happens to the photon when a polariton forms?

When a photon passes from the vacuum to a medium such as water, a polariton forms in the water which carries the energy from the photon at a slower speed through the medium. The polariton being ...
8k views

### Why aren't rainbows more common?

Why are rainbows relatively rare? On any given day, there are billions of water drops in the air of varying sizes and dispersions, all of which light is passing through and refracting. What physical ...
996 views

### Can refractive index be used interchangeably with wave impedance?

Everything I've been taught so far for EMR and waves at an incidence has been using the refractive index. for example, the reflection coefficient for a wave normal to an incident is R = ((n1-n2)/(...
299 views

### Why does dispersion of light behave in the opposite way for diffraction compared to refraction?

When blue light is shined through a diffraction grating it bends less than a longer wavelength, let's say red light. The shorter the wavelength the less it is bent by diffraction. When the same ...
217 views

### Confused with image and object distance in lens

I am not sure why S is negative in this image. How do we determine whether it's negative or positive?
70 views

### Number of images [closed]

A glass slab of refractive index n=2 has left spherical of radius 10cm and right surface plane.From both surfaces refraction as well as reflection takes place.A point of object P is placed at a ...