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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Fabry Perot Etalon - changing wavelength and plate distance

Given reflectivity $R = 0.75$, an etalon is used as an interference filter, transmitting light of wavelength $4.3\mu m$ at normal incidence. The full width half maximum is about $\Delta \lambda = 0.2 ...
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Image formation at surface of water

Consider a lake full of water which has an object immersed in it. Now, if an observer was at the surface at a sufficient distance so that the light ray from the object is internally reflected, should ...
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reflection at intersection of 2 mirrors

Consider 2 mirrors which intersect at an angle. If we draw a light ray intersecting the mirrors at their point of intersection, how will it reflect? What will be the normal at that point?
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How can results from classical optics be obtained from QFT?

Recently it came to my mind, that I have some basic knowledge about QFT and know im principle how to calculate scattering amplitudes (at least for the $\phi^4$-theory), but have no idea how to ...
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group velocity in non dispersive medium

In a non-dispersion medium, phase velocity is equal to group velocity of waves. Consider a free quantum particle moving in one dimension say $\text{x}$ axis. There would be matter waves associated ...
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31 views

Using Optic Lens to Simulate Distance

I have an actual scenario, where I have to align a particular electronic optical device to two objects in the distance (2-3 km away), forming a right angle at the point where the optical device is. ...
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59 views

Differences between absorption, transparency, reflection, and emission

Can someone help me conceptualize the differences between a photon's involvement with absorption, transparency, reflection, and emission? To be more specific, my current understanding of the matter ...
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Quick question on convolution - Diffraction through a pair of slits

We know that the fourier transform of the amplitude function (in terms of $y$) gives you the amplitude function (in terms of $\theta$) Consider a pair of triangular slits: Fourier transform of ...
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29 views

Optics, What is a Foil?

I was using a program for simulating optical elements; mirrors, gratings, foils, crystals, slits, and zoneplates are what it mentioned. Does anyone know what a foil is in terms of optics? I know what ...
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70 views

Why does silver have such a strong UV resonance compared to other metals?

Related: Why did high quality mirrors use aluminum coatings instead of silver? After reading Chris White’s and LDC3’s comments in the above related link, it got me wondering about silver’s atomic ...
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Analytically transform a spherical wave into a planar one

Is it possible to transform a light spherical wave front or another wave front with a known behaviour into a planar one? Say I have the position of a point light source, and I can approximate it by ...
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Why did high quality mirrors use aluminum coatings instead of silver?

I have two questions on mirrors. I’ve read that in the past quality mirrors were coated with silver but that today vacuum evaporated coatings of aluminum are the accepted standard. When I look at ...
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29 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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101 views

Observer looking out through the window of a train [duplicate]

When travelling by a train, it seems that the nearby objects move in the opposite direction(which I can explain) but the distant objects appear stationary. I can't explain this. By the concept of ...
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28 views

Optical Waveguides with grating

I have some problems about mode analysis in grating-coupled waveguides,Would you please introduce me a useful book about wave propagation in these structures.
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1answer
75 views

Omega-frequency or pulsation?

I'm reading a book about optics in English. However, I speak a different language and have a problem with distinction. What does $\omega$ mean? $\omega=1/T$ or $\omega=2\pi/T$ What is the ...
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158 views

Why is the phase velocity used in the definition of the refractive index?

I'm aware of the so-called group index but why is the phase velocity used in the standard definition of the index of refraction? What advantage does this offer?
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A photon travels in space for 10 billion years. What are the odds it will arrive here without interacting with a atom on the way?

Space isn't a perfect vacuum and I wonder how an image of a galaxy can travel billions of years without becoming diffused by photon collisions with space matter?
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Why are the bounds to the permittivity $\epsilon$ a circular arc in the complex plane?

I'm reading this paper which is essentially about connecting the complex permittivity $\epsilon$ with the microstructure of a thin film. They talk about how you can place limits on the possible values ...
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76 views

Reflection & Transmission curves of waveguides

I have simulated a grating-coupled waveguide in Comsol Multiphysics, the waveguide consists of 2 dielectric layers and air as the cover of waveguide. I have excited the modes of this structure by a ...
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Why does one get an illusion as moon following him?

When you run or ride bike at night if you observe the moon you feel like he moves along with you as the same speed you are going. Why?
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Light, Fourier Transforms, Spherical Harmonics

Mathematically, I'm having trouble understanding where we can use what with light. I read somewhere on this site that Huygen's Principle is effectively just taking an expansion of a wave onto the ...
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1answer
113 views

Covering centeremost slit of a N slit diffraction grating - what happens?

For an N-slit diffraction grating, the distance from a maxima to a minima at order p is given by $$\delta \theta = \frac{\lambda}{Np}$$ What happens to this width when the centremost $\frac{N}{2}$ ...
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58 views

How to specify BRDF measurement

As a person who will be using the scattering measurement results (in Zemax), I was asked to prepare the specs for the BRDF measurement. However I've never done it until now, so help would be greatly ...
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82 views

Conservation of energy (or lack thereof) in Doppler cooling [duplicate]

I did not find my question answered elsewhere, so here it is. I'm doing a project in my first optics course, and we are reading a bit about Doppler cooling. I understand that a laser is tuned to a ...
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1answer
78 views

Geometric optics- Sign conventions

Why do we need to use the sign convention again in the mirror equation while solving numericals when we know we have already used a convention while deriving the mirror equation? The question is not ...
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40 views

Polarizing beam splitter

I'm searching for basic literature or papers introducing the action of polarizing beam splitters with single photons. Unfortunately the most books and papers only focus on usual beam splitters. The ...
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Blonde hair looking green at certain angle

I have a friend who has blonde hair. And when look at an oblique angle, there's a tinge of light green in her hair. I've heard that the copper ion in pool water can make blonde hair green, but her ...
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Direct optical observation of the Arago spot: what would one see?

The Arago/Poisson spot is an excellent example of a constructive interference of diffracted light. In the traditional experimental layout, you observe projected light on the screen. The theory in this ...
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157 views

Sign convention for mirror and lens formulas

I have just started learning optics at school and my teacher derived the lens and mirror formulas. While doing so, she applied the sign convention for u,v and f and arrived at the final expression. ...
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1answer
125 views

How was the Michael Jackson hologram accomplished?

There have been a few presentations now in which a live stage performance was simulated by what was described as a hologram. The most recent example of this was the Michael Jackson "appearance". How ...
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1answer
47 views

Reflections in a double-glazed window

Recently I observed reflections in a double-glazed window. I wondered that the double reflections were not the same if I changed my point of view. For example the two images of a candle would overlap ...
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Does the speed of medium affect the path of light?

Let's say I shine a laser from a stationary medium into a moving medium (suppose the water is moving very quickly) perpendicular to the interface and back to a stationary medium like this: (Note: ...
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1answer
28 views

Electric Field and Magnetic field of Guassian beam [closed]

The center of the gaussian beam in glass has a beam power of 1 mW and a beam radius of 20 μm (micro meter). The wavelength of the light $\lambda_0$ is 1550 nm. How can I find the electric field E ...
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44 views

Single Photon Hits A Linear Polarizer, What Happens?

If a linear polarized single photon strikes a linear polarizer such that its polarization is at 45 degrees to the polarization axis of the polarizer, what happens? There is a nearly 50% chance that ...
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41 views

Infinite plane wave and ray vectors

I want to clear my mind on one basic optics thing: If I have a point source some distance away from a lens, the position of the image formed can be found using traditional geometrical optics ray ...
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80 views

Numerical aperture (NA) of an optical fiber

Numerical Aperture (NA) (for fiber optics) is usually used to denote the acceptance cone for a multi-mode fiber. Does NA also describe the expansion of light emitted from the end of a fiber? I have ...
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1answer
37 views

Different degrees of freedom with RGB, CMYK and Frequency

Ok, so I understand the eye has 3 different types of receptors and I've seen the process of converting from RGB to CMYK. However if in physics I can specify a color using a single number (its ...
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3answers
92 views

Is there an atomic level explanation for diffraction of light around opaque aperture?

It has always been a hard time understanding the phenomenon of diffraction of light around opaque objects. Hoe does it happen? Why does transparent objects do not diffract light? What quantum ...
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38 views

Snells Law: Does the $k$ vector change on the boundary between mediums?

I was using Waves - Berkley Physics Volume III, and in explaining Snell's Law the author claims that as a wave is on the boundary between glass and air (going from glass to air) that the number of ...
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1answer
60 views

New focal point of converging light through a concave lens

Suppose I pass rays of already converging light through a concave lens. The rays are equally centered on the lens such that the original focal point is through the lens and centered on the lens axis. ...
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1answer
34 views

Color of macroscopic objects on molecular level

Macroscopic objects either reflect, or transmit, or absorbs electromagnetic waves. Assume now we have, say, a red apple exposed to the usual white light. The red light is apparently reflected from ...
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1answer
46 views

Is glass considered as a linear optical medium?

My research, which is mainly related to communication, involves the use of optical sources (mainly lasers). However, my background in photonics and optics is not yet solid, so my question might be a ...
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1answer
54 views

Relationship between Polarizability and Conductivity

I've seen in the literature the relation: $\sigma (q,\omega) = \frac{i e^2 \omega}{q^2}\chi(q,\omega)$ where $\sigma$ is the conductivity and $\chi$ the polarizability. However my attempt to derive ...
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1answer
48 views

What is the amplifying medium in a laser diode?

I know it seems like a trivial question, but I can't seem to find the answer anywhere. So - what is the amplifying medium in a laser diode? Meaning: In a classical laser resonator, there a substance ...
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60 views

Black holes: Behaviour of light near an event horizon

Electromagnetic waves travel mostly in vacuum medium, in outer space, but sometimes in gaseous media, such as in gaseous atmospheres involved in nebulae. If electromagnetic-waves come anywhere in the ...
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What happens when a polarized light get reflected by a rough dielectric material?

I have a polarized light (lets say p polarized) which happens to undergo scattering when it is obstructed by a rough opaque dielectric material. What will happen to polarization? Will some part of it ...
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31 views

Do plasmons depend on the ambient EM field?

Imagine a situation: There's an illuminated metal slab in vacuum. Normally, there are some plasmons created running all over the slab. What would happen if we had turned a giant magnet near the slab? ...
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45 views

What is light localisation?

Reading about plasmonic nanoparticles I faced the term "localised light". How can one localise light? What are applications of it?
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Are all fluorophores dipoles?

Lately I'm reading about surface enhanced fluorescence. In many articles I can see that fluorophores are called "dipoles". Is it because that they can be modelled by a vibrating electric dipole? Or ...