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 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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97 views

Is it possible to focus the sun in such way?

Imagine the sliding part of the mirror is controlled by computer and opens on intervals. Is it possible to increase the power of the beam by making it bounce between the mirrors thus going through ...
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2k views

Eye sensitivity & Danger signal

Why are danger signal in red, when the eye is most sensitive to yellow-green? You can check luminosity function for more details...
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67 views

What's the difference between Raman scattering and second harmonic generation in crystal?

As far as I know, the Raman scattering is from the stokes and anti-stokes scattering that the laser light interact with molecular vibrations. So we know that ""laser light interact with molecular ...
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166 views

What electric field vector should I use for modeling unpolarized light?

Regardless of computational cost, light is a kind of electromagnetic wave, so it can be simulated with Maxwell's equations. If we want to simulate light with Maxwell's equations, we need to express ...
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899 views

Why doesn't my pinhole camera work?

We all know that light travels in straight a line, which can be proved by pinhole imaging as in the picture shown : But when I'm doing this little experiment with an apple, no matter how I change ...
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184 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 ...
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590 views

How to make mirrors give more authentic image of myself

My friend bought two normal mirrors from some shop probably IKEA, looking like this one: My images are different from the two. One is a little fatter and shorter, and the other a little thinner and ...
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52 views

When polarized light hits a polarizer, what happens to the polarization which is not transmitted?

It is typically said that in polarization of light only those waves can pass through a polaroid which has a plane of vibration parallel to the axis of polaroid. My question is: what happens to the ...
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64 views

Third order optical mixing

It's pretty straight-forward to visualise second-order non-linear optical mixing processes in which two waves of frequencies $\omega_{1}$ and $\omega_{2}$ mix up to generate new waves of different ...
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136 views

Stimulated Emission

In the case of stimulated emission we always see that one photon goes into the gain medium and two photons come out. How can this conserve energy?
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79 views

Quality loss when adding more components to a telescope?

I would think this would be inherently true, but I'm curious: (Assuming the highest quality amateur instruments are used.) Is quality lost when, say, adding a T-mount adapter, diagonal or any other ...
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2k views

Why should optical fibers be thin?

What are the reasons that optical fibers have to be thin (small radius of the fiber)? Is there a good picture which explains this in detail?
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133 views

Is there a way to increase the speed of light itself?

When light enters materials it slows down due to its refractive index (due to absorbing and re-emission of photons). But, is there a way to increase the speed of light itself? Can there be some ...
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104 views

When one can make telescope that can distuingish 1 mas?

When one can make telescope that can distuingish(angular resolution) 1 mas object by angular diameter? If already possible, tell the name of telescope/observatory. How to calculate angular resolution ...
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195 views

Effects of surface roughness on specularity

Say you have a piece of glass, which looks specular if propery cut/polished. But if you sand the surface using say sand paper, it will look hazy and glossy. I'm wondering how much surface roughness ...
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1answer
672 views

Beam splitters- Direction of use

There are two cases I'm asking about. The square in the middle is a cube beam splitter in the same orientation for both cases. We are looking at the beam splitter from the top. In the first case, ...
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20 views

For resolving different objects, are there any alternative coefficients to the one used in the Rayleigh criterion? (which is 1.22)

http://en.wikipedia.org/wiki/Angular_resolution#Explanation It's the point where you can't distinguish between the maxima and the first minima. But could there be cases where you have a more ...
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1answer
144 views

Why (infra-)red light is not used in diagnostics?

I noticed that human body conducts red visible light quite well. A hand placed over a powerful red lamp seems to be semi-transparent while over any other color it does not. Possibly the light ...
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1answer
76 views

Is it possible to extract the index of refraction from reflection/transmission measurements like this?

I'm trying to manipulate some data to see if my analysis method is reliable: I want to use transmission and reflection measurements within a certain wavelength range to get the index of refraction ...
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61 views

Can polarization effect the coherence length?

I'm taking an optics lab in which I'm required to construct an interferometer, and measure the wavelength of a laser, and the coherence length of the light emitted from a candle fire. Now, I've been ...
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94 views

Is there a way to create a flickering frequency to be dependent on speed of the person looking at it?

Is there a way to make a screen or a road sign flash at different rates, depending on the velocity of the observer looking at it? I would like to achieve a state where two observers going at ...
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2answers
100 views

Why is $\vec j\cdot \vec e$ the joule dissipation?

I always see $\vec j\cdot \vec e$ as Joule's dissipation and I don't understand why. For example, if we have a uniform electric field $\vec e=e_o\vec u_x$ and we release an electron in it, it will ...
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459 views

Why do polarized sunglasses remove (most) reflections on car windows?

Why do polarized sunglasses remove (most) reflections on car windows? I know that both lenses of polarized sunglasses are polarized in the same direction and I can see that reflections in my own ...
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1answer
57 views

Linearizing Quantum Operators [duplicate]

Possible Duplicate: Linearizing Quantum Operators I was reading an article on harmonic generation and came across the following way of decomposing the photon field operator. $$ ...
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190 views

Light refraction and causality

One way how to look at refraction by a dielectric medium like water or glass is that (phase) velocity of light decreases because it is the wavelength rather than the frequency of the light which ...
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1k views

What is the effect of polarization on diffraction by a narrow slit?

Consider the well known demonstration of diffraction by a narrowing slit. (See for example the demonstration at the 30 minute mark of this lecture at MIT by Walter Lewin) It is my (possibly mistaken) ...
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How do contact lenses work?

I understand how telescope, microscope and glasses work. But how do contact lenses work?
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203 views

Didn't Newton's Corpuscular theory fail to explain reflection?

In 1637 Descartes gave the corpuscular model of light and derived Snell's law. This Corpuscular model of light was further developed by Isaac Newton in his famous book entitled OPTICKS and because of ...
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99 views

Why does a light wave invert at a boundary with greater index of refraction?

Is there a reason why a EM wave reflects invertedly when it meets a boundary point with a greater index of refraction. In the case of ropes, if remember correctly, the reason why it inverts is to ...
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286 views

Does diffraction occur before interference?

In the double slit experiment, light passes through two slits and the waves interfere and form an interference pattern. A single slit is required for diffraction. So, I was thinking about whether ...
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95 views

What happens if an already excited electron gets hit by another photon (lasers)?

Slightly vague title but it is the best I can do. My question stems from some interest in how 3 stage lasers function. A photon from the pumping source comes in and strikes a atom in the active ...
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1answer
432 views

How far can the human eye see? Any ending point or infinite?

How far can the naked human eye see if unobstructed? (straight ahead on perfectly flat land). Is there a stopping point or is it infinite when you look in the sky? Is there any situation that the ...
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1answer
434 views

Three polarizers, 45° apart

If light is passed through two polarizing filters before arriving at a target, and both of the filters are oriented at 90° to each other, then no light will be received at the target. If a third ...
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423 views

How does this trick with mirrors work?

Imagine two mirrors, set touching each other at right angles to one another. There is a 90 degree arc in which reflections can be seen, and a person standing in that arc can see himself reflected in ...
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1answer
157 views

Optics Paradox?

Imagine we have two lens, one convex and one concave, spaced in such a way that the convex lens is before the concave lens. Now each lens has its own focus length and both are spaced such that the ...
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242 views

Redirecting light beams from beam splitters

I'm doing a project where I am taking a laser beam and sending it through a beam splitter. As I understand, approximately 50% of the light will go pass through and 50% will be reflected. So this means ...
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285 views

Does a fluid's temperature affect the way light passes through it?

For example, if I were to supercool water would it's refractive index still be 1.33 or would it be 1.31, the same as water-based ice even though it's still in liquid form?
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603 views

Hartmann mask based collimation

Is there a detailed description for a Hartmann mask based collimation process? I've been told by a friend that is possible to collimate an SCT by placing a three round holes Hartmann mask at the ...
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1answer
256 views

Fermat principle: which index of refraction?

I am somewhat puzzled by a common formulation of the Fermat principle (light travel time), because it contains index of refraction related to phase velocity while light travel time through a slab of ...
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1answer
70 views

What means: distortion <XX% in lens spec?

I'm going to buy a lens and I would like to understand what means "distortion < XX%"? It's a vari-focal 10-60mm lens and mentionned distortion <12-1%. According to my understanding @ 10mm focal ...
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1answer
443 views

Calculating Fraunhofer diffraction patterns

How does one calculate the Fraunhofer diffraction pattern for the following arrangement of slits: |...|...........|...| ..a.....3a......a (Four slits arranged linearly, spaced a distance a, 3a and ...
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425 views

Why is the observed signal the convolution of the true signal with the instrumental function?

Imagine we are observing a star. The light coming from a star enters an optical instrument that will give us some observed data, such as the spectrum of light say. What we observe is not the true ...
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396 views

Numerical software to manipulate a light beam in its plane wave representation?

Any light field can be expressed as a sum of plane waves. Such an ensemble of plane waves is called the plane wave spectrum of the light field. The plane wave spectrum is the Fourier transform of the ...
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788 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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370 views

Lens design - max lpmm, monochromatic light

How can I approach this task: I need to design diffraction-limited lens for monochromatic light (~1nm line width, so I guess no need to correct chromatic aberrations), geometry aberrations are also ...
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1answer
263 views

Which lens parameters determines it's format?

I'm working with a megapixel sensor with a 1/2" format. I would like to know which parameters have to be taken into account in order to design a lens that can be fit with 1/2" format. The light ...
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36 views

Why a minus in the equation of a paraxial plane wave?

paraxial plane wave = $\exp{(-jkz)}$ for waves propagating to the right I can't figure out why it's not $\exp{(+jkz)}$. Any help would be greatly appreciated, thank you.
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182 views

Fermat's principle to prove the law of reflection

Fermat's principle tells that a light ray will follow a path from point $A$ to point $B$ so that the optical path length of this path is an extremum over neighboring paths. I wanted to use this ...
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104 views

Diffraction by a lens

The fraunhoffer treatment of circular apertures yields a diffraction pattern of circles, with the first minimum (dark ring) at an angular radius of $\theta$ where $\sin(\theta)=1.22\lambda/b$, where ...