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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Are Fresnel lenses widely used for solar electricity? If not, why not?

I was just wondering why Fresnel Lenses are not widely used in the production of solar electricity. Their use there would mean that you could produce heat within a fraction of a second, up to a few ...
23
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4answers
2k views

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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4answers
5k 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
62 views

Why human and most of vertebrates cannot see Near-Infrared light (720nm-1500nm)? [closed]

On daytime, the surface of Earth is illuminated abundantly by light of spectrum from 250nm-1500nm, that includes near-ultraviolet spectrum (250nm-380nm), visible spectrum (380nm-720nm) and ...
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1answer
58 views

What is causing the separation of light in this image?

Reflection of keychain LED light on Macbook Pro (2014) screen I have also observed this phenomenon on my mobile phone and on a tablet. I assume this means it is somehow related to backlit ...
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2answers
106 views

Light-Matter Interaction and Object's Appearance

I am taking a course in Computer Graphics, and the teacher said we could put materials in there main categories: mirror like glossy or specular diffuse He suggested that the law of reflection is ...
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2answers
1k views

Relation between Radiance and Irradiance

I know the radiance is expressed as $$\text{[Radiance]} = \frac{W \cdot m^2}{\text{sterad}}$$ and $$\text{[Irradiance]} = W \cdot m^2$$ But what's the relation between theese two quantities? Is the ...
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1answer
80 views

Mode groups in an optical fiber

I know what modes in an optical fiber mean but what are exactly mode groups in an optical fiber? From what I read until now, I have the impression that modes that have close propagation constants ...
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2answers
136 views

Quantum theory of light

What's the scattering matrix for a PBS (polarization beam splitter)? Is it just unitary? If one polarization never couples into another polarization (then there's a lot of zeroes in that 4x4 matrix) - ...
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0answers
19 views

Reason behind formation of doublets in diffraction spectrum

like if you see is Sodium (and also in Mercury), there are two discrete lines of Yellow color.. What's the reason behind formation of doublets?
3
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1answer
524 views

Why would an object appear a different size when in water?

A friend of mine has a homework question and we're having some trouble figuring out what physical mechanisms come into play for this. An underwater swimmer sees a spherical air bubble that appears ...
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1answer
38 views

Luminance from multiple light sources

I have a LED diode: Given Luminance intensity [I] of $1.85$ cd. I want to have Luminance [B] from the light source of $75 \ {\rm cd/m^2}$. From $B=I/S$, where S is light source plane area, I get ...
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0answers
17 views

Can the granular quantum nature of light be used to engineer a maroscopic optical phenomena?

Today we have optical metamaterials and metasurfaces: materials and surfaces that are made of unit cells with an approximate size of tens of nanometers, that can that interact with light and can have ...
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1answer
54 views

Two layers of glass reflection related to wave interference [closed]

A highly reflective mirror can be made for a particular wavelength at normal incidence by using two thin layers of transparent materials of indices of refraction $n1$ and $n2 (1 < n1<n2 ) $on ...
0
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2answers
42 views

How to chose right lens for concentrating IR signal? [closed]

I am looking for the right acrylic lens. Since will be buying at least 1000 pieces I don't want to make any mistake. I want to concentrate the signal from IR LED in a 1cm diameter tube at one point ...
2
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0answers
41 views

What is the relation of scattering, extinction and absorption cross sctions with scattering parameters?

In optics and electromagnetics, they frequently calculate the extinction, scattering or absorption cross sections of a single particle (e.g. a sphere). Scattering cross section which is the ratio of ...
3
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2answers
173 views

Fiber optics with broadband, incoherent light

I wonder if someone could help clarify waveguiding with broadband, incoherent light please. If we take a telecomms fiber, which is single-moded above ~1.4 μm and couple a laser beam in, we assume ...
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0answers
20 views

What is the minimum bend radius of a square optical fiber on a microfluidic chip interface?

I want to make a microfluidic chip with colorimetry cuvettes with 100um square optical fibers coupled to the side of them. They should bend at a 90 degree angle to exit the side of the chip in a ...
2
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2answers
60 views

How to make a rotating linearly polarized (not circular polarization) beam from a single beam?

One way to make a linearly polarized beam rotating at frequency $\Delta f\approx10\mbox{MHz}$ is by combining two circularly polarized beams, one left-handed and one right-handed, and where one beam ...
3
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2answers
89 views

Why is there no dark band below a rainbow?

I've read articles about Descartes' theory of the rainbow and I can understand why there is a dark band of about 8 degrees (Alexander's band) between the primary and secondary bows: for all the water ...
2
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1answer
40 views

Good resource for geometric optics

I'm looking for a good resource (preferably a book) on geometric optics. I am thorough with the basics (the mirror formula, lensmaker's formula, thin lens formula, etc). What I want is something that ...
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1answer
44 views

Describing a single photon with creation and annihilation operators

Since I am not fully aware of the creation and annihilation operator formalism for single photons, I want to ask, if the following is correct: I am considering a photon in the vacuum which travel ...
0
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1answer
18 views

if you're wearing goggles, will the light beam appear to travel straight?

if person A is outside a pool and person B is inside a pool with goggles, won't the light beam travel closer to the normal inside the pool but then away from the normal when it enters the goggles (due ...
2
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0answers
39 views

Why isn't Zemax showing a tilt on the wavefront on my telescope design?

Attached is a Zemax file Zemax File for an afocal telescope system. When i tilt the field by an angle of 2 degrees (In green) I would expect a wavefront tilt at the "Image " plane, however when I ...
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1answer
28 views

Do TN and IPS displays are subject to diffraction?

Sometimes displays with the same resolution, diagonal and aspect ratio appear to have different level of sharpness . In optics there is this concept of diffraction and if you can lower your ...
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1answer
29 views

why an immersion lens is called so in Ion Optics?

In Ion Optics, an immersion lens is composed of two planar apertured electrodes. My question is why it is called an 'Immersion" lens? I know that an Einzel lense has three or more electrodes. But ...
4
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1answer
59 views

Why does sea colour differ from place to place?

If you notice the colour of sea changes from place to place. At some places it is of blue or green and even different in beach. What must be the reason?
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1answer
34 views

Solving Optics problem with and without differentiation result in different results

In a recent class of physics-calculus, I and my friends were discussing about a certain problem about optical lens. The problem was: "I a certain laboratory setup, there are a lens of focus $f$, an ...
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0answers
13 views

Autocollimator independence from lens to measuring object distance

i have been reading about metrology for a while, however in the angle measuring section, when introducing the autocollimator it says the distance from the lens to the object doesn't introduce error, ...
0
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1answer
38 views

Why do pores make ceramic opaque?

I want to know how a ceramic transparency is mostly affected by the pores, grain boundary, second phases etc. present inside of it, but the major contribution is due to the pores. Let's consider the ...
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2answers
42 views

Why does electromagnetic refraction happen?

Why does refraction happen? In high school textbooks, it is stated that it happens because the speed that electromagnetic waves propagate in the media change. But why cant they continue propagating in ...
0
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1answer
145 views

Semiclassical description of EM waves reflection from metallic surfaces

Imagine an EM wave impinging on a metal. Fresnel's formulas tell us that no wave can propagate through the metal, or that the transmitted field is an evascent wave with some penetration depth ...
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0answers
20 views

Particle collision: relationship of incident and reflected particles [duplicate]

A photon traveling through a curved fiber optic cable advances by reflection, yes? If each reflection is the product of a collision between the incident photon and, say, a wall particle that ...
2
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1answer
36 views

Could a lens be used to melt sand into glass

Could I melt sand, like that inside a sand dune, into glass using a focused lens? What factors would affect a lens melting sand? I was thinking you could use a lens to melt sand, to gather sand ...
2
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1answer
38 views

Single photon pulse and its electromagnet field

I describe the temporal distribution of a single photon pulse in an interferometer experiment in vacuum via the Gaussian function $\psi$: $$ \psi(t) = \tfrac{1}{(2\pi\sigma^2)^{1/4}} \text ...
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2answers
37 views

Lowest detectable power of a laser?

What is the lowest power of a laser beam which is still detectable? More precise: If the intensity of my laser beam is reduced by a factor of $10^{-8}$, can I still detect it? Of course this depends ...
5
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4answers
576 views

Why is an opaque body opaque?

When does a body qualify to be called an opaque body? Is it anybody which cannot let visible light through it or is there any other definition? And when and how does a body allow radiations through ...
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0answers
33 views

Increasing the volume of a object in a photograph

I have two images which look like this --- These images are two views of a calibration object --- the white die that you see hanging in the middle. The problem is that, the die is too small and ...
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0answers
25 views

Third-order dispersion of glass

When working with short laser pulses, it is important to compensate the dispersion of a pulse passing through a material because it changes the pulse's shape. The effect of dispersion can be described ...
3
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2answers
83 views

Shack-Hartmann wavefront sensor concepts, pupil conjugate planes?

I am just starting to looking at the application of wavefront abberommtery to measure abberations in the human eye. I am confused over the pupil conjugate planes, do you use relay lenses to image the ...
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0answers
36 views

Reflectivity of gases

According to the principle of the conservation of energy, the following is true for an object: emissivity+reflectivity+transmittance=1; where emissivity=absorbtivity according to Kirchoff. When ...
10
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2answers
379 views

a weird image of sun

Have you ever notice the sunset's image in the sea? It's like long light path to the end of the horizon! I've attached a sample of this: How can we explain this? I know that it can happen even in ...
3
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1answer
18 views

How to construct matrix to apply U(2) beam splitter to a N dimentional Beam

So I am trying to read this paper (no paywall here). In this the formal construction of a matrix $T$ is given as The product of matrices is equivalent to setting up experimental devices in ...
2
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0answers
16 views

Circular diffraction onto uneven surface

I'm trying to figure out how to solve for a surface using a circular diffraction. I have a pinhole diffraction that I'm projecting into a surface and I'm trying to figure out how to derive the shape ...
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0answers
36 views

Two thin lenses in contact [closed]

Two thin lenses with same focal length are in contact. what is the resultant focal length? Options a) f b) 2f c) f/4 d) 4f My Answer By both plotting the light ...
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0answers
9 views

How can an interference pattern encode both the angle of incidence and relative phase in a hologram?

For example - there are two "object" beams, both 180-degrees out of phase with the reference beam, which hit the recording plate at angles of incidence of 30-degrees and 90-degrees respectively. ...
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0answers
30 views

How can Young's double slit experiment explain the wave nature of light?

I've been reading about wave theory of light and the famous experiment performed by Thomas Young. But how does this experiment prove that light is a wave ?
0
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2answers
43 views

Twinkling in sunlight reflections

A question that covers optics and possibly biology/physiology: looking out my window, I see the Sun reflecting off car windshields in a distant parking lot. The very bright reflections are distinctly ...
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1answer
28 views

Construct classical computer using classical light

Quantum light (i.e. photons), linear optics, adaptive measurements and feed forward can be used to build an efficient universal quantum computer. ref: Knill et. al. 2001. Clearly the above resources ...
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1answer
47 views

Wavefront sensor specifications Shack-Hartmann

Why is the dynamic range of Shack-Hartmann wave-front sensors (As seen in the first image below) quoted in wavelengths and not in angles? I thought that one of the most important aspects of the ...