Change in the direction of propagation of a wave when its transmitting medium changes.
2
votes
1answer
54 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 ...
0
votes
1answer
35 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 ...
0
votes
0answers
26 views
Computation of refractive index of the upper atmospheric air using pressure, temperature and humidity measurements
Upper Air Sounding Systems (UASS) measure the properties of the atmosphere typically till a vertical height of 30 km from Mean Sea Level (MSL).
The balloon-suspended sensors used over here measure ...
0
votes
0answers
15 views
Clarify an assertion about refracted and reflected waves in Feynman
In The Feynman Lectures vol. 1, chp. 33, Feynman is disucssing about intensity of light and says that:
The principle that we must understand is as follows. The currents that are generated in the ...
0
votes
2answers
70 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 ...
60
votes
4answers
11k 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 ...
0
votes
1answer
21 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 ...
0
votes
0answers
12 views
Does the speed of a light wave decrease in Earth's atmosphere? [duplicate]
Light wave is made up of photons, which exchange energy with the atmospheric molecules.
1
vote
2answers
19 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.
...
1
vote
1answer
41 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 ...
2
votes
2answers
107 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 ...
2
votes
1answer
24 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 ...
0
votes
2answers
39 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 ...
0
votes
1answer
32 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?
...
1
vote
1answer
128 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, ...
-1
votes
0answers
27 views
Why is there no purple in the rainbow? [duplicate]
I see from here that while green and orange are how we perceive actual wavelengths of light, purple is a mixture of red and blue.
Why is there this difference? Green is a mixture of blue and yellow. ...
0
votes
1answer
55 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 ...
0
votes
1answer
34 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 ...
0
votes
1answer
70 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 ...
0
votes
4answers
73 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 ...
0
votes
0answers
27 views
Speed of light when not travelling in a vacuum [duplicate]
My question is about the speed of light when not in a vacuum. What is happening when the light travels through water? Are the photons being constantly abosorbed and emitted by the water molecules (so ...
8
votes
4answers
842 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 ...
0
votes
0answers
16 views
Negative Fresnel coefficient
Apparently a negative coefficient for the reflection fresnel coefficient, for any of these two
$$
r_{||}=\frac{\tan(\varphi^t-\varphi)}{\tan{(\varphi^t+\varphi)}}
$$
$$
r_{\perp}=\frac{\sin{(\varphi^...
1
vote
0answers
51 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 ...
2
votes
2answers
69 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 ...
1
vote
0answers
26 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 ...
1
vote
1answer
37 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)?
5
votes
3answers
209 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 ...
0
votes
0answers
19 views
Solving multiple refractions with virtual objects?
On doing several questions in which refraction through a glass slab, convex lens, etc. is dealt with, the question is solved by splitting the slab or lens into two surfaces and dealing with the ...
0
votes
1answer
37 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 ...
3
votes
1answer
61 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 ...
1
vote
1answer
57 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 ...
1
vote
0answers
30 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 ...
4
votes
2answers
225 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 ...
1
vote
0answers
24 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 ...
3
votes
1answer
35 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 ...
0
votes
1answer
49 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?
1
vote
1answer
61 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 ...
24
votes
3answers
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?
1
vote
2answers
39 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 ...
1
vote
1answer
35 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 ...
2
votes
2answers
145 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 ...
0
votes
0answers
20 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 ...
4
votes
1answer
261 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 ...
3
votes
1answer
37 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.
0
votes
2answers
75 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 ...
0
votes
0answers
54 views
Refractive index in presence of two immiscible liquids when apparent depth and real depth of object is given?
A jar containing two layers of immiscible liquid has a coin at the bottom.The two layers A,B are 6 cm and 8 cm deep.A has a refractive index of 1.5 and the apparent depth of the coin is 9 cm.A is the ...
0
votes
0answers
19 views
Derivation of group velocity as a function of refractive index dispersion (solved) [duplicate]
How can I derive the expression $$v_g=\frac{c}{n-\lambda_0 \frac{dn}{d\lambda_0}}$$ in the wiki page? I know we need to use chain rule, but I can't quite get the terms of $dn/d\lambda$ in the ...
40
votes
5answers
7k views
Why aren't rainbows more common?
Why are rainbows relatively rare? On any given day, there are billions of water drops in the air of varying sizes and dispersions, all of which light is passing through and refracting. What physical ...
0
votes
1answer
74 views
Can refractive index be used interchangeably with wave impedance?
Everything I've been taught so far for EMR and waves at an incidence has been using the refractive index.
for example, the reflection coefficient for a wave normal to an incident is
$$R = ((n1-n2)/(...
