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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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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2answers
82 views

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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8 views

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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0answers
50 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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2answers
2k views

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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0answers
46 views

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 ...
3
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1answer
111 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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0answers
51 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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2answers
74 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
53 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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0answers
37 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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0answers
58 views

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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0answers
22 views

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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1answer
88 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
120 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
34 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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4answers
210 views

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
27 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 ...
2
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1answer
37 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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1answer
37 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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1answer
45 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 ...
3
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1answer
31 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
82 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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1answer
50 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. ...
3
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1answer
32 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
43 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 ...
2
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1answer
43 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
43 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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1answer
56 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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0answers
32 views

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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0answers
30 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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2answers
43 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?
3
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2answers
45 views

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 ...
4
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2answers
91 views

Is a Perfect/Lossless Mirror possible?

In traditional mirrors, some of the input light is absorbed by atoms in the mirrors surface and are 'lost' as heat, degrading the quality of the reflected image. Could this loss be compensated by an ...
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0answers
84 views

Optical mode leakage through a layer of gold

The geometry of my semiconductor device is given below. The blue regions are gold, the grey ones - gallium arsenide (n-doped to $2.9 \times 10^{15} \mathrm{cm^{-3}}$). The dimensions are μm, i.e. it ...
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2answers
61 views

Distance between two light rays of a beam in a material.

Why is it that the distance between two light rays changes as they pass from one material to another? It must have something to do with the change in refractive index, but to me it seems the ...
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1answer
59 views

How should we put two lens?

How should we put two converging lens in order for parallel rays passing between both lens to remain parallel?
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1answer
47 views

Topological phase in Laguerre-Gaussian transverse mode

Why is the topological phase in a Laguerre-Gaussian transverse mode is the sum of orbital angular momenta per photon, and why is it quantized?
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3answers
118 views

Duality behavior of light and effect of system scale on its behavior [closed]

Does an electromagnetic wave that makes by antenna behaves purely as wave for all the times? or it can change its behavior as photon? and does the scale of system effect on behaving as EM wave or ...
3
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2answers
57 views

What makes a material a good lens for CO2 lasers?

I read on Wikipedia that zinc selenide and germanium make good lenses for $\mathrm{CO}_2$ lasers. My question is, Why?
2
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1answer
79 views

In what applications are lasers necessary vs. just convenient?

I’m trying to understand, given the wide array of current laser applications: Which applications actually require laser characteristics, as opposed to just use lasers because they are the most ...
2
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1answer
43 views

Help calculating field of view for ball lens I just bought

I have a 5 mm (diameter) solid ball lens that I intend to place in front of a 36mm X 24mm camera sensor (I have already made preparations for the image to be focused and for the sensor to not be ...
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1answer
28 views

Learning material on optical computing

I'm looking for guidance to choose material for a self-study of photonics, biased towards optical computing recent advances. My background is of undergraduate level electrodynamics, quantum ...
177
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7answers
10k views

How does light bend around my finger tip?

When I close one eye and put the tip of my finger near my open eye, it seems as if the light from the background image bends around my finger slightly, warping the image near the edges of my blurry ...
2
votes
2answers
81 views

Anodized aluminium reflectivity at 10.6 um

I wonder how I can model anodized aluminium reflectivity in ray tracing-based optical simulation. I know that the parts my company is using are anodized to get covered with a ~20 um (as specified) ...
10
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2answers
348 views

a wierd 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 ...
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1answer
74 views

Yet another Young Double Slit Experiment

If I have a laser light incident on the double slit at an angle O < 90 what kind of interference pattern will I see? Will i see the same with less intensity or different pattern?
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3answers
319 views

What happens to the index of refraction of a lens if placed in water?

What happens to the index of refraction and focal length of a lens that is initially in air that is then placed in water?
3
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1answer
335 views

Diver view of refraction

I'm studying the refraction in optics. If a red light monocromatic beam of red light (700 nm) passes from air to water it becomes with a wavelenght of aprox 526 nm. So, my question is: How is going ...
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1answer
22 views

optics biconvex and plano convex

What is the resultant focal length If a biconvex lens is cut into half and then the resulting 2 plano-convex lens arranged in such a way that the plane surface of one faces the curved surface of the ...