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Why is a monochromatic wave temporally coherent for all time delays $\tau$?

The Wikipedia reference you give, in the chapter [Temporal coherence], does not actually give a mathematical definition of how this "temporal coherence" is supposed to be defined! If we take ...
Jos Bergervoet's user avatar
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Why is a monochromatic wave temporally coherent for all time delays $\tau$?

According to the Wiener-Khintchine theorem, the degree of temporal coherence of a light wave is proportional to the Fourier transform of the wave's spectrum. Mathematically: $$\mu(\tau)\propto FT(I(\...
Lagrangiano's user avatar
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0 votes

Why is absorbance calculated as $\log_{10}(1/R)$ and not $1-R$?

Absorbed light cannot be measured because it no longer exists as light, so we quantify absorption by measuring the light that suffered other fates, and assume the remainder is absorbed. If we assume ...
Donald Dahm's user avatar
1 vote

Is it possible to see thermal columns?

The refractive index of air is often taken to be one, but in fact it's slightly higher. Under normal conditions it's about $1.0003$. To a good approximation the refractive index minus one is ...
John Rennie's user avatar
1 vote

Amplitude of light in double slit experiment

The amplitude is the square root of the intensity. Which square root? Well, for the double slit experiment you may consider that the bright bands' amplitudes alternate in sign. Positive or negative ...
John Doty's user avatar
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3 votes

Inconvenience of speed of light in optic fiber

This is really engineering more than physics. Vast resources have been expended developing methods of purifying glass to make optical fibers with very low loss. This allows us to have fibers that lose ...
The Photon's user avatar
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0 votes

Phase shift in a film

The reason is that you have to consider the wavelength of the light inside the film which is different from that in vacuum/air. In particular, when light travels through a media with refractive index ...
Tommaso Gallo's user avatar
0 votes

What exactly happens to a light ray that is incident on the vertex of 2 mirrors inclined at some angle

In geometrical optics there is no such a thing as a single ray by itself, there are only rays of finite ray bundles (pencils). A ray is one of the infinitude of orthogonal trajectories of the ...
hyportnex's user avatar
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0 votes

What exactly happens to a light ray that is incident on the vertex of 2 mirrors inclined at some angle

Mathematically, it depends at which angle you hit the corner. You can show that the ray will be reflected symmetrically along the angle bisector. In a physical mirror, the corner would not be a ...
paulina's user avatar
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0 votes

Imaging and illumination plane in microscope

I think both of the previous answers are mostly correct but fail to understand what you are struggling with. There is only one light source and it is divergent. In Kohler illumination the microscope ...
Noah's user avatar
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0 votes

What is the apparent location of a real image formed by a lens?

If you are viewing real image with your eye further away from the real image than the least distance of distinct vision (ie further than the near point) then the answer is give here, Real images and ...
Farcher's user avatar
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2 votes

What is the apparent location of a real image formed by a lens?

Real images look like real objects. Think about it: your eyes cannot distinguish, having access only to the light rays entering it, a real object from a real image. In both cases, your eyes receive ...
HTNW's user avatar
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5 votes

What is the apparent location of a real image formed by a lens?

The figure describes the situation, but in words, the real image will be formed on the near side of the lens (same side as observer). This was pointed out in the question. It will appear to the ...
ad2004's user avatar
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1 vote
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Question about lasers

A laser contains an active medium that produces light such as a gas discharge or a PN junction. An energy source excites atoms. They produce photons when they decay. Decay may happen spontaneously. Or ...
mmesser314's user avatar
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1 vote

Amplitude of light in double slit experiment

In microwave engineering (which will give the same calculation in classical optics) the light intensity is calculated in the far field from electric and "effective" magnetic current on the ...
Pierre Polovodov's user avatar
0 votes

Why the dielectric permitivity matrix of lossless media is symmetric?

As long as the medium is linear and reciprocal, i.e., there are no (magnetic) effect like the Faraday effect, also lossy media have a symmetric permittivity tensor, which has complex elements and is ...
freecharly's user avatar
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1 vote

Difference between permittivities $\varepsilon_\text{opt}$ and $\varepsilon_\infty$?

Very often, in materials physics, we are interested in the relative permittivity at optical frequencies which is usually denoted by $\varepsilon_\text{opt}$ or $\varepsilon_\infty$. The notation $\...
hft's user avatar
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0 votes
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Demonstration of constant radiance for Lambertian Surfaces

We have the function $f(\theta)=I_0\cos\theta$ for which we wish to find $\partial_{A\cos\theta}f(\theta)$. First, rewrite $A\cos\theta$ as $u$, and then we will express $f$ in terms of $u$: $$\begin{...
Riley Scott Jacob's user avatar
0 votes
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Ambiguities in optical waveguide modes

I understand the problem in the following way (please comment if it is not what you want): you have a infinite slub - a sandwiched layer inside a dielectric. One dimension is infinite in the model ...
Pierre Polovodov's user avatar
1 vote

A question about circularly polarized light

In addition to my2cts answer showing how circularly polarized light is detected, I would like to add the reason for this phenomenon. EM radiation can be polarized in the next way. In a polarization ...
HolgerFiedler's user avatar
0 votes

Complex part of second-order susceptibility in nonlinear optics

The main argument to ignore second order (and most even) nonlinear processes is because historically, centrosymmetric systems have negligible even order susceptibilities ($\chi^n$ where n=2,4...) and ...
ondas's user avatar
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-4 votes

A question about circularly polarized light

Sorry I agree with your colleague. Circular pol light is typically a mix of 2 linear polarizations created by certain crystals/materials, the circular thing is a mathematical construct where we can ...
PhysicsDave's user avatar
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0 votes

Can eyeglasses slowly "burn" one's eyes similar to using a magnifier glass?

So long as you don't look straight at the sun, eyeglasses can't burn the eyes. Eyeglass lenses can be used for burning things like leaves, but this can only be done with convex lenses (those that ...
Aristocratic Jack's user avatar
0 votes

Why do sun glasses shield more sunlight from a specific angle?

It's probable that the sunglasses are polarized. LCD screens (those that laptops, smartphones, tablet devices, and most other screens use) also are polarized, meaning looking at the screen through a ...
Aristocratic Jack's user avatar
4 votes
Accepted

A question about circularly polarized light

With two circular and one linear polarisers you can do it. Use an unpolarised light source. First show that half the light passes the two circular polarisers when aligned and none passes when they are ...
my2cts's user avatar
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0 votes

A question about circularly polarized light

Circular polarized light is photons in helicity eigenstates. I think the left vs. right is a bit confusing, but that is just convention. A photon in the spin state: $$ \chi_{\pm} = |S=1, S_z = \frac{\...
JEB's user avatar
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1 vote
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What is a convex-concave lens?

You may want to compare to a regular convex lens, where the lens is curved outwards on both sides. Concave is like the side of a bowl you fill with soup and it stays in the bowl. If you flipped the ...
ad2004's user avatar
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0 votes
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What is the relationship between frequency and photocurrent?

It is possible that the term "Intensity" is causing some vagueness here. First, it should be emphasized that one photon produces one photoelectron (according to Einstein, as mentioned in the ...
ad2004's user avatar
  • 1,118
2 votes
Accepted

When solving a paraxial Helmholtz equation ... ? Amplitude vs Wave function

I'm not sure what is the par-axial Helmholtz equation. But consider the function $$ a(x,z) = A(x) e^{i k z}, $$ and consider the Laplace equation $$ ∆ a(x,z) = \nabla^2 a(x,z) =\frac{\partial^2 a(x,y)}...
Nitaa a's user avatar
  • 268
15 votes

How does the mirror know what’s behind the paper?

The other answers are quite right, of course, but I thought it might be helpful to know the comic has a second page in which Aki Hayakawa explains how mirrors work. This prompts a rather... crude ...
Sturrum's user avatar
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0 votes

How does the mirror know what’s behind the paper?

The interesting thing here is how our eyes perceive light.Light has different wavelength,for this context, consider you give all different colour of light we perceive a specific code, we will call it ...
Dheeraj Gujrathi's user avatar
27 votes
Accepted

How does the mirror know what’s behind the paper?

Perhaps a diagram would help? Excuse my poor artistry: Clearly, you can see that there is a trajectory a ray can take which starts at the top of the egg, hits the mirror, and then intersects your eye....
Riley Scott Jacob's user avatar
5 votes

How does the mirror know what’s behind the paper?

Is it not just a matter of at which angle you are and how is constructed the reflection? The reflection is just the brain trying to reconstruct the position of the object by continuing the ray of ...
Syrocco's user avatar
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0 votes

Reflection due to wave nature of light

PERFECT MIRROR One can think of the reflection as constructive/destructive interference of waves (see Figure 1). In order to reach a detector (e.g., human eye), light waves from a point light source ...
Capo Mestre's user avatar
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1 vote

Spectral colors in filled wine glass

I think one way to look into this is to use other pictures to understand what is happening optically. The picture you provide is, unfortunately, not that great because of a few factors: The picture ...
ondas's user avatar
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2 votes

How to measure the direction of circular polarization of single photons?

Be careful of the term "circular polarization" and the misleading graphic in the video by PBS and O'Dowd. Circular polarization is typically just a mix of 2 linear polarizations (such as ...
PhysicsDave's user avatar
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1 vote

How to measure the direction of circular polarization of single photons?

I don't have a link to the Clauser paper, but the following from Aspect et al (1981) uses exactly the same technique. "Following Freedman and Clauser, we used the 4p''S, -4s4p... cascade in ...
DrChinese's user avatar
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0 votes

Pointing flash at LCD television creates a weird diffraction effect

Perhaps there are repeating little structures with a shape like this: The edge diffractions could in that case explain the six rays that we see. And if the pitch is in the order of 100$\mu$m, colored ...
Jos Bergervoet's user avatar
1 vote

Radiation through optical windows

Your second approach is much better. If you have enough light power to make negligible the thermal radiation of the inner shield (including the inner window), then the light power transmitted to the ...
Gilbert's user avatar
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0 votes

Radiation through optical windows

I believe I was approaching this in the wrong way and the Stefan-Boltzman equation is not what is needed here. I decided that I should have used the incoming light intensity along with the known ...
Cones's user avatar
  • 31
1 vote

Reflection due to wave nature of light

Both previous answers still rely on ray optics for their arguments while OP clearly wants to know how to explain things via wave description. I will attempt at giving an answer based on waves. Imagine ...
José Andrade's user avatar
0 votes

Is there a filter which can directly convert sunlight to microwaves?

You can convert sunlight to microwave, but I wouldn't call it a filter and why waste the energy by sending it back out of the atmosphere? Use the energy or store it.
Bill Alsept's user avatar
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0 votes

Is there a filter which can directly convert sunlight to microwaves?

Bad... The problem with this "solution" is that water molecules existing in the atmosphere broadly absorbs microwave range EM radiation and so they will be heated (like water in microwave ...
Agnius Vasiliauskas's user avatar
1 vote

Diffraction of a double slit where the slits are far apart

Your equation is obtained from the standard Fraunhofer diffraction conditions which require the assumption that the size of the aperture is much smaller than the distance from the aperture to the ...
Vincent Thacker's user avatar
-2 votes

Reflection due to wave nature of light

A perfect mirror conserves the direction of the light rays. Therefore reflected light can be imaged by a lens. A rough surface on the other hand scatters the rays in all directions. It can the no ...
my2cts's user avatar
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0 votes

Reflection due to wave nature of light

When light hits a mirror, it follows a specific law known as the law of reflection. This law states that the angle of incidence (the angle between the incoming light ray and the normal, which is an ...
Shantanu Binekar's user avatar
0 votes

Why is the shorter the wavelength, the smaller the object you can image? and vice-versa?

Here is a simple mental picture which may help. Draw yourself a wave chain of sine waves going across the page. Now imagine inserting an object into the trough between two maxima in the curve. To get ...
niels nielsen's user avatar
2 votes

Spectral colors in filled wine glass

This is due to dispersion. The refractive index of the glass (and of the wine) differs for the different wave lengths that are present in the white light of the sun. This is the same effect that ...
Sebastian Riese's user avatar
2 votes

Spherical aberration of lens

Both lenses shown have spherical aberration. For many uses, the spherical aberration of a plano convex lens is small enough not to matter. For other uses, it isn't good enough. An ideal lens would ...
mmesser314's user avatar
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-2 votes

Light waves can't have a wavelength

Panagopoulos, D. J. (2018). Man-made electromagnetic radiation is not quantized. Horizons in world physics, 296, 1-57.
Michael Luhr's user avatar

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