Optics is the study of light, and its interaction with matter. It includes topics such as imaging systems, fiber optics, lasers, quantum optics, and more.
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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 ...
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3answers
911 views
What really cause 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 is related to the permeablity and the permitivity of the material. But this is not what I'm interested in, ...
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4answers
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Why does the sky change color?
Why the sky is blue during the day, red during sunrise/set and black during the night?
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1answer
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Why can you see virtual images?
In optics it is widely mentioned real images are projectable onto screens whereas virtual ones can only be seen by a person. Isn't that contradictory? I mean in order to see the virtual image it has ...
4
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2answers
200 views
How do you calculate power at the focal point of a mirror?
I'm a Mechanical Engineering student and I'm working on my senior project, so I need help. My project is about designing a solar dish having a diameter of 1.5 meters and a focal length of 60cm. so at ...
4
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2answers
790 views
What happens to light in a perfect reflective sphere?
Let's say you have the ability to shine some light into a perfectly round sphere and the sphere's interior surface was perfectly smooth and reflective and there was no way for the light to escape.
If ...
2
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2answers
333 views
Where is a good place to learn (classical) optics?
I need to learn basic optics for a high school academic competition. Does anyone know any good places, preferably free and online, to learn the basics of optics, like lenses, angles of incidence, ...
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5answers
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4answers
432 views
What longest time ever was achieved at holding light in a closed volume?
For what longest possible time it was possible to hold light in a closed volume with mirrored walls?
I would be most interested for results with empty volume but results with solid-state volume may ...
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4answers
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Why glass is transparent?
Once I asked this question from my teacher and he replied "because it passes light", "and why it passes light" I asked and he said "because it is transparent".
Same question again, Why glass is ...
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3answers
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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 ...
2
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3answers
492 views
Recently publicized experiment on destructive interference between two laser beams
Recently I've had several non-physicist friends ask me, independently of each other, about an experiment where two collinear laser beams destructively interfere along a certain length. Everybody wants ...
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5answers
306 views
Trapping a lightray
Given a solid whose interior is a hollow sphere with perfectly reflecting mirrors. A small hole is drilled in the sphere and a photon is sendt in at some angle. Will it always eventually exit through ...
19
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3answers
580 views
Why wet is dark?
When something gets wet, it usually appears darker. This can be observed with soil, sand, cloth, paper, concrete, bricks ...
What is the reason for this? How does water soaking into the material ...
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2answers
853 views
Make a semi transparent mirror with copper
The question:
How would you make a semi transparent mirror (50% reflection, 50% transmission) with glass with a layer of copper. For light $\lambda$ = 500nm Try to be as realistic as possible
What ...
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2answers
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How does Fraunhofer diffraction depend on the orientation of the sides of a lens?
Matt in his answer on What does a hexagonal sun tell us about the camera lens/sensor? mentions
Incidentally the number of (distinct)
points to the star is equal to double
the total number of ...
8
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6answers
1k views
How come an anti-reflective coating makes glass *more* transparent?
The book I'm reading about optics says that an anti-reflective film applied on glass* makes the glass more transparent, because the air→film and film→glass reflected waves (originated from a paraxial ...
4
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4answers
561 views
Optical explanation of images of stars?
Very often when viewing pictures of the cosmos taken by telescopes, one can observe that larger/brighter stars do not appear precisely as points/circles on the image. Indeed, the brighter the light ...
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2answers
356 views
Human perception of distance
When we see things around us, distant objects look smaller to our eyes than nearby objects do.
Is there any physics-related reason why our eyes or brain perceive things like this?
Or if this is ...
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7answers
881 views
Is it possible to blur an image in such way that a person with sight problems could see it sharp?
If someone has short or long sight, is it possible to tune image on a computer monitor in such way, that a person could see it sharp as if they were wearing glasses? If not, will 3d monitor make it ...
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3answers
387 views
What are these rays that appear in photograph of sun?
In many images of light emitting objects we see such rays. Why do they appear ?
What is the math behind their number and direction?
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5answers
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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
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Why does paper become transparent when smeared with oil but not (so much) with water?
When I smear oil onto a scrap of paper and rub it in, the paper becomes quite transparent; but when I attempt the same with water it doesn't as much. Why?
5
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5answers
801 views
Why aren't there compression waves in electromagnetic fields?
I just started learning about optics, and in the book I'm reading they explain how the electrical field caused by a single charged particle could be described by a series of field lines, and compare ...
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4answers
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Is it possible to observe interference from 2 independent optical lasers?
It seems that if the coherence length of a laser is big enough, it is possible to observe a (moving) interference picture by combining them. Is it true? How fast should photo-detectors be for ...
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1answer
252 views
What causes a ring-like image around light of the moon?
I just encountered an interesting image in sky.
As you can see in following images there was a ring-like image around light of the moon.
I don't know if it was clouds but it was looking like it is far ...
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2answers
252 views
Is apparent horizon curvature lesser due to refraction of light in the atmosphere?
I have encountered this claim while searching for sources answering " Can we see the curvature of earth from the top of world's tallest building? ".
Wikipedia article on horizon claims (with no ...
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3answers
368 views
formula for transparency of very thin film of metal
Is there formula that gives transparency of very thin film of given metal (tens of nanometers) to the visible light/light of given wavelength ? Which properties of metals are needed for the formula ?
...
3
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4answers
147 views
Rainbow around Sun
From the perspective of a person, a rainbow is formed when the Sun is behind the person, and there is a critical angle made by the rainbow.
However, on several occasions, usually at noon when the Sun ...
3
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2answers
549 views
Propagation of light in transparent media: absorption and reemission or scattering?
In the two Phys.SE questions What is the mechanism behind the slowdown of light/photons in a transparent medium? and Why glass is transparent? transparent media were discussed. But I'd like to clarify ...
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4answers
483 views
Why are color values stored as Red, Green, Blue?
I learned in elementary school that you could get green by mixing blue with yellow.
...
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1answer
137 views
Calculate the distance between two points from iPhone Camera
I want to calculate the distance between two objects using an iPhone camera.
Suppose I'm standing with my iPhone 10 feet away from the objects. Now, I want to calculate the distance between those ...
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0answers
53 views
Trigonometry in the plane mirror [closed]
I was trying to solve a problem taken from an Physics Olympiad when I came across a curious and complex mathematical expression. I can not prove with what I know so far about mathematics, does could ...
34
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1answer
3k views
Why does a window become a mirror at night?
In day, when you look in the room through the window out, you can clearly see what happens outside. At night when it's dark outside but there's light inside you can look in the window but it becomes a ...
11
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1answer
439 views
Formulation of Transformation optics using a Material Manifold
Dear Community,
recently, Transformation optics celebrates some sort of scientific revival due to its (possible) applications for cloaking, see e.g. Broadband Invisibility by Non-Euclidean Cloaking ...
12
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1answer
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How are photons “consumed”?
I have very little background in physics, so I apologize if this question is painfully naive.
Consider the following thought experiment: an observer is in a closed room whose walls, floor, and ...
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3answers
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Light “diode” and 2nd law of thermodynamics
If I had a light "diode" - an object that only allowed light (at least for a range of frequencies) to travel through it in one direction, would this necessarily allow violations of the 2nd Law of ...
9
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4answers
558 views
Nonlinear optics as gauge theory
the widely used approach to nonlinear optics is a Taylor expansion of the dielectric displacement field $\mathbf{D} = \epsilon_0\cdot\mathbf{E} + \mathbf{P}$ in a Fourier representation of the ...
6
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2answers
268 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 ...
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2answers
810 views
What does an atom radiate: a wave packet or a single photon?
What does an atom radiate: a wave packet or a single photon?
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3answers
637 views
Is one way glass possible?
I am not talking about mirrors, just a plain window made of glass like material. Would it be possible to allow light pass only in one direction but not the other?
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3answers
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Is there a limit to the resolving power of a mirror telescope?
Like, if you flattened out Ceres to a 1 mm iron foil telescope mirror with 20x the surface area of the Sun, could you resolve details on the surface of an exoplanet? Could you make it arbitrarily ...
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3answers
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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 ...
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3answers
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How can I determine transmission/reflection coefficients for light?
When light rays reflect off a boundary between two materials with different indices of refraction, a lot of the sources I've seen (recently) don't discuss the relation between the amplitude (or ...
2
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4answers
276 views
How are we able to view an object in a room with bulb..?
This is a very basic question on optics. How are we able to view an object kept in a room with a bulb?
From what I understand, light rays from bulb will hit the object and some colour will be ...
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5answers
2k views
Why can you have shiny black objects?
Knowing black is supposed to be the "color" (I don't want to get into the color/hue/shade debate, please) that absorbs light. how does one manage to have shiny black surfaces? I know about "gloss ...
7
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1answer
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How are classical optics phenomena explained in QED (color)?
How is the following classical optics phenomenon explained in quantum electrodynamics?
Color
According to Schroedinger's model of the atom, only particular colors are emitted depending on the type ...
5
votes
1answer
83 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 ...
5
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3answers
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Can anyone explain to me why light is not dispersed into a spectrum through a parallel glass slide, but only through a prism?
The question pretty much sums up what I need to know. Why is it that light only gets dispersed into a spectrum when travelling through two non-parallel sides(like a prism) and not through something ...
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2answers
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Accuracy of various optical instruments
I understand that this may not be the type of question allowed here, but I'm not sure. Feel free to close this if you feel that it shouldn't be here
I'm planning on carrying out a certain set of ...
