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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Polarizability and the Clausius-Mossotti Relation

There seems to be a fairly large inconsistency in various textbooks (and some assorted papers that I went through) about how to define the Clausius-Mossotti relationship (also called the ...
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116 views

cgs Gauss' system of units

I had never seen this system until today, and I'm really confused. I've read the wikipedia article about it but I still don't know how to change between this and the international system. For example, ...
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5answers
4k 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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1answer
202 views

Is a holographic recorder able to capture a large full color picture? [closed]

Is it practical to attempt to build a 3D hologram generator that is full color and big enough to recreate a watermelon full size? If so, is real-time control feasible?
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159 views

Are EM waves scattered the most when the wavelength and the obstacle have a similar size?

I heard that when the wavelength and obstacle are similar in size, the scattering is the greatest. Is this true?
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2answers
168 views

Smaller Airy disk with another lens?

Is it possible to reduce the airy disk size produced by one lens with another lens placed after the previous one? For example, parallel ray incident on first lens L1 (without aberration), then there ...
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2answers
112 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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2answers
220 views

Can a detuned laser can excite an atom? How?

Can a detuned laser can excite an atom? If so, how is this possible?
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3answers
108 views

Trapping EM radiation [duplicate]

Is there a material which can allow light (or any other EM radiation) to pass through from one side as if it is transparent but its other side reflects light like a mirror?
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525 views

How does a Fresnel rhomb work (half and quarter wave plate)?

How does a Fresnel rhomb work (half and quarter wave plate)? I am aware of birefringence, which creates a phase shift of $\Delta\phi=\dfrac{2\pi\Delta nL}{\lambda_0}$. But this doesn't explain how a ...
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0answers
14 views

Image formation [duplicate]

What is the real cause behind the formation of an image? It is explained as" when rays of light focus at a point image is formed." So here we have two events, one focusing of light and another ...
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1answer
138 views

Is this mental picture of photon correct?

What is exactly meant by a statement like "there are about 400 photons per cubic cm in certain region"? Should I mentally picture this as 400 discrete photons enclosed in that volume, each moving at ...
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1answer
50 views

Circular polarisation

If we have a planar and harmonic EM wave, with $B$ field: $$B=A\left(\begin{array}{c} 1\\ i\\0 \end{array} \right)e^{-i(\omega t-\vec k\cdot\vec r)}$$ and with it's corresponding $E$ field. This is ...
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2answers
170 views

Gravitational distortion of an object's diameter, at a distance,

Does the curvature of space-time cause objects to look smaller than they really are? What is the relationship between the optical distortion and the mass of the objects?
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1answer
88 views

Is there a formula for determining the focal point of a sphere?

I guess this is the same as for cylinders, when light is shone through parallel to the cross-section, but Google-ing this only turns up lenses like the ones used in glasses. I'm looking for something ...
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1answer
181 views

Seeing a mirage through mirror?

Okay, I am not really good in physics (rather terrible), but nonetheless. So, I was just wondering if you can see a mirage, is there something special in our eyes that we can see it or what? I mean, ...
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1answer
300 views

Where did this equation come from ∠I+ ∠E = ∠A+ ∠D?

$\angle I +\angle E=\angle A+\angle D$ Angle of incidence + angle of emergence = angle of prism (Normally $60^\circ$) + angle of deviation. If their sum is not equal,we made personal error in doing ...
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1answer
136 views

Photon in a weighted superposition of states

Consider an experiment that produces photons in an entangled state such as $1/\sqrt{2}(|{H,H}\rangle+|{V,V}\rangle)$. The photons are in a superposition of horizontal and vertical polarization, and ...
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2answers
1k views

What is the minimum optical power detectable by human eye?

If one is in complete darkness, what is the minimum optical power that the eye can "see" (let's say in 500-600 nm range). I found that for 510 nm, 90 photons can be detected ...
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1answer
219 views

How can some optical microscopes measure height differences of different sample planes with nanometer accuracy?

I could use last week an optical microscope, didn't seem special in any way, 50x magnification, image viewable per a CCD camera on a computer screen besides through the ocular. But the software of ...
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2answers
832 views

All mirrors always shrink to 50% scale?

I have this geometric optics exercise here, in which a man is looking at himself in a mirror. Determine the minimum height at which the bottom of the mirror must be placed so the man can see his ...
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2answers
13k views

Maximum theoretical bandwidth of fibre-optics

Ignoring hardware at either end and their technological limitations, what is the maximum theoretical bandwidth of fibre optic cables currently in use / being deployed in a FTTH type situations? I ...
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2answers
709 views

Why does light not refract when incidented perpendicularly?

I had read that light does slow down in glass because photons interact with atoms in glass. They are absorbed and re-emitted and during this phenomenon it's speed decreases. See also this and this ...
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344 views

Liouville's theorem and gravitationally deflected lightpaths

It is customary in gravitational lensing problems, to project both the background source and the deflecting mass (e.g. a background quasar, and a foreground galaxy acting as a lens) in a plane. Then, ...
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1answer
586 views

What is the effect of refractive index of an object for imaging?

My Question is as follows. What is the effect of refractive index of an object for imaging (Photographs by high speed camera) on its size and shape information incurred from image? Lets say , I ...
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0answers
193 views

Weakly Guiding Approximation

I was reading a chapter on Fiber Optics and I encountered Weakly Guiding Approximation. I am reading John M. Senior and it says ...
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3answers
2k views

What causes insects to cast large shadows from where their feet are?

I recently stumbled upon this interesting image of a wasp, floating on water: Assuming this isn't photoshopped, I have a couple of questions: Why do you see its image like that (what's the ...
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2answers
492 views

How to calculate the height and length of a reflected ray?

I barely know anything about optics, so I could use some help about how to go about solving this problem. If I have a ray of light at a certain height from the optical axis, propagating at an angle, ...
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3answers
2k views

Why is visible light used in Optical fibers (instead of other EM waves)?

Why aren't other electromagnetic waves used in optical fibres instead of visible light? Is it because the wavelength of light fits the internal reflection/refractive index of the material used for the ...
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2answers
4k views

Where does energy go in destructive interference? [duplicate]

I have read that when two light waves interfere destructively, the energy contained within is transferred to other parts of the wave which have interfered constructively. However, I am having some ...
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2answers
560 views

What is a two-photon process?

I am reading some introductory materials on modern optics, in which they mention two-photon processes everywhere. I know fundamental optics and a bit on quantum mechanics. Can anyone explain in a ...
9
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1answer
7k views

Two mirrors facing each other

What happens when you place two mirrors facing each other? Is it possible to have an infinite amount of reflections?
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1answer
416 views

Eikonal approximation for wave optics. Why follow the unit vector parallel to the Pointing vector?

The description of the passage from wave optics to geometrical optics claims that light rays are the integral curves of a certain vector field (the Pointing vector direction, normalized to 1). Here ...
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1answer
185 views

Why is spectral sensivity of a photodiode expressed in A/W

Can someone explain me the meaning of the A/W unit of the photosensivity when reading a spectral response function of the wavelength characteristic of a photodiode?
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2answers
72 views

Optical trapping problem

Can we make light slower by applying optical trapping (I mean applying laser beam to lower the speed of light)?
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1answer
673 views

calculating focal length of meniscus lens

As I read about telescope, distance between objective lens and eyepiece must be equal to addition of their focal lengths. D = F1 + F2 I used one of the eyepiece ...
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28 views

Speed of Light in a Medium [duplicate]

For light travelling in a medium with refractive index greater than one: The "average" speed of light is slower than the speed of light in a vacuum. As far as I know, the instantaneous speed of light ...
2
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1answer
129 views

Factors that make beam divergence worse after refocusing

A beam of light of width $W$ and wavelength $\lambda$ with divergence that is diffraction-limited is refocused with an optical element placed at a distance $D$ from the beam source. Will the refocused ...
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1answer
340 views

Computer-Generated Holograms: I'm completely lost. How are they physically implemented?

I have been reading about holography, and I think I understand the general concept, but one thing that has me completely lost is how computer generated holography works in practice. I think I get the ...
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2answers
225 views

How are X-rays focused? Specifically in XRD. Well do they even focus X-rays in XRD?

I read in a government website that reflecting an x-ray from a parabolic mirror followed by a reflection from a hyperbolic mirror results in focusing the x-ray, but this was for astronomical purposes. ...
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0answers
70 views

How to calculate the correct coordinates from a distorted video of a projectile?

I am working on a high school project that is related to projectile motion. I am exploring how exactly the position of the center of mass affects the trajectory of a long but thin, javelin-like ...
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1answer
72 views

Erratic light spot in optical projection

I once had an old microscope, that included a projection screen that could be mounted instead the eyepiece. It showed a quite decent palm-sized image. Now I have a new microscope, and removed the ...
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1answer
115 views

Ratio of distance between mirror and person

In perspective of a given example, if a man was to stand $2\ m$ away from a mirror which was $0.9\ m$ in height and was able to see his full reflection, what would the height of the mirror have to be ...
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2answers
745 views

Can't seem to reconcile geometric optics and wave optics

I was looking at a physics situation involving light, and I can make the correct derivation assuming light is a ray of a given intensity (geometric optics), energy conservation checks out, everything. ...
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2answers
66 views

Optical refocusing efficiency

What is the material for optical focusing that produces the less diffraction losses? Suppose one have a sequence of serial optical elements $R$ that keep refocusing a beam of collimated light, each a ...
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2answers
566 views

Irradiance (or intensity) of an electromagnetic wave

Is the irradiance (or intensity) of an electromagnetic wave given by \begin{equation} I = \left<\|\mathbf{S}\|\right>_{T} \end{equation} or by \begin{equation} I = ...
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1answer
136 views

Can we project a 4D world using 3D video technology?

Traditional movies, TV, etc, faithfully show our 3-dimensional world using 2 dimensions. So can we have a movie that shows a 4-dimensional world using 3D technology?
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1answer
426 views

3D movie glasses making white light look red and blue

While waiting for a 3D movie to start, I was playing with the glasses they give you. I understand each lens has different polarized filters, so the left and right superimposed images on the screen go ...
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3answers
347 views

Beam waist at extremely long distances

A beam of light of wavelength $\lambda$ and width $W$ needs to be focused at a distance $D$ to a spot not bigger than $w_S$, which stands for 'width of sail'. Now, the diffraction limit says it ...
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1answer
608 views

How does light get into a stable optical cavity in the first place?

It is supposedly possible to trap a beam of light bouncing back and fourth between two mirrors in a stable configuration. As I understand it, this means the configuration will prevent further spread ...