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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Fresnel to Fraunhofer limit

I'm puzzled about what happens when distance L from obstacle to screen is continuously increased from a small value (Fresnel diffraction) to infinity (Fraunhofer diffraction). Please consider four ...
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23 views

Why do clothes look darker or change color when they get wet? [duplicate]

Clothes can look darker or change color when they get wet. Why does this happen?
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17 views

The first term of Stokes Vector of natural light is zero?

Consider the electric field of a beam of natural light: $$ E(r,t) = E_0 \cos(k·r+wt) $$ Since this beam of light is natural, the vector E has all the components possible that satisfies: ...
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2answers
29 views

understanding the Yellow shadow

In my Living room when I turned on Blue LED lights, in the shadow behind chairs when I turned on white light I see the yellow color, what exactly happens here this is due to interference of light or ...
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379 views

How do I find the right lens for my laser?

I purchased this line laser recently and I'm running into a bit of an issue. The laser shoots out at a 120 degree angle which is perfect. However, once the laser spreads to about 4.25 inches, I need ...
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42 views

Is there more to the future of computers than quantum computers? [on hold]

Some time ago the computer of the future was with many processors. The academic world had multicore computer's since the 80s and the BeBox was an early commercial multicore. Now we hear that the ...
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37 views

With the new time cloak technology could it be possible to stop time for everything except one person

So I was just reading up on some new research on national geographic from the Cornell University scientists and it seems that they've managed to bend waves of light around something to hide it from ...
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1answer
42 views

What exactly is an image?

When we say several rays meet to form an image, what is that which is formed? Is it an arrangement of unknown entities? What exactly am I looking at when I see my image in a plane mirror?
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20 views

How does a, halftone screen work?

Forever I've seen explainations that say a halftone printing image is made by photographing through a screen. But I have yet to see explained how that does the trick. Apparently the screen is placed ...
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19 views

Spectrometers for atmospheric studies [closed]

In what ways are spectrometers needed for atmospheric studies? And which spectrometer is more suitable for atmospheric studies, Fabry-Perot spectrometer or Michelson spectrometer? Are both 2-D and 3-D ...
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21 views

What could cause the gradual loss (or change) of power in a CO2 laser over a long period (e.g. a year)?

For example, if it were a 10W CW CO2 laser that were used for ~45 minutes per day over a period of a year. Would you expect a slight reduction in power with age? Does the dissociation of CO2 occur ...
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2answers
28 views

Arrow that changes direction home experiment

I saw this cool optical effect in a experiment on Youtube: https://www.youtube.com/watch?v=G303o8pJzls Could anyone explain to me why the arrow points in the opposite direction? I have read ...
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1answer
45 views

Huygens' Principle During Reflection: comparing wavelets from before reflection with wavelets from during reflection

I was recently reviewing geometric optics, during which I read about Huygens' Principle and how it could be used to prove the Law of Reflection from the "light is a wave" viewpoint. I'll quote what I ...
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1answer
43 views

Is the IoR of water exactly $4/3$?

The index of refraction of water is commonly cited as $n \approx 1.33$, to varying numbers of decimal places. I've never seen a decimal expansion for this value with any digit other than $3$ past the ...
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1answer
43 views

Why does larger permittivity of a medium cause light to propagate slower?

I was wondering about what physically happens when light is transmitted through a non-magnetic medium. Specifically, I’m trying to visualize how materials slow down light as the electromagnetic wave ...
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1answer
28 views

Can a polarizing beam splitter cube be used to replace two polarizers?

I have a design for a setup to look at the light reflecting off the back of the human retina. I would like to remove any specular reflection that occurs at the cornea. At the moment the idea is to use ...
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1answer
27 views

Cause behind bending of light in refraction [duplicate]

I know that refraction is caused due to change in speed of light but why does it bends? I also know that during refraction frequency is constant and wavelength is decreased since speed slows down. But ...
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25 views

Question: calculate deviation of light due to gravity by imagining it as a change in optic medium [closed]

Q: light bends due to gravity. we assume that due to gravity of a point object of mass $M$ , it changes the refractive index of vaccum at distance $R$ from the object as $$n = 1 + \frac{2GM}{RC^2}$$ ...
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2answers
46 views

How do HUD optics create readable text so close to the eye?

The human eye has a minimum focal length of about maybe 50-80mm. Most Heads Up Displays (HUDs) are much closer to that, so how is the text they display visible without being horribly out of focus? ...
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43 views

Is there a way to cancel lens effects?

If I had 2 identical lenses, and put the two facing each other in oposite directions, would their effects be cancelled? Is there a way it could be done, maybe with fresnel lenses, so that it would ...
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4answers
81 views

How to measure the size of a laser dot?

I'm not a physicist, that's why I'm asking you if there is maybe an easy way (e.g. a mathematical law) to measure the size of a laser dot, or its diameter. The setup It contains a laser, a high ...
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1answer
24 views

How can I make an optical circulator?

I need to a single mode 1550 optical circulator at my lab. I have a varied supply of components, but no circulator. Any idea how I can make one myself? Perhaps using coupler and isolator? Thanks. -D ...
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991 views

Can spectacles converge sunlight to an extent that it burns the eyeball?

I need to know whether wearing spectacles can cause optical harm. I saw a movie where one pair of glasses was placed on table exposed to sunlight, then the sunlight converged and focused to a point ...
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1answer
49 views

light is allowed to pass through transparent objects? [duplicate]

light passes through transparent objects like water and glass ,where in case of glass the molecules are more tightly packed or concentrated then to it allows light to pass, Why?(yet reflection occurs ...
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14 views

Electro-Optics, Where to Start Studying

I have an opportunity for pursuing my Doctoral studies in a Electro-Optics domain. I have been chosen because I fulfilled the other criteria to secure the opportunity. I still have quite a lot of time ...
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3answers
51 views

Why diffraction is related to wavelength not amplitude

For diffraction, the wavelength of the incident beam should be in range magnitude of the slit length, but why the amplitude is not related to the length of the slit?
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1answer
26 views

A very basic question about optics and figuring out focal length

Focal Length of a lens - I was told that as an approximation I could simply put a sheet of paper with text on it on a table, hold the lens above it, and when I can see the text most clearly, the ...
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Why does Threshold current of laser increase with the increase in temperature?

Why does Threshold current of laser increase with the increase in temperature? I know that at the same current level, the power is higher at lower temperature but why?
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How do I derive Sommerfeld's solution of the case when the incident ray is aimed obliquely to the edge of the screen?

I already know that the Sommerfeld's solution to this problem is conical. But internet does not show me the simple of exact derivation of this solution. How do I solve this problem?
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1answer
46 views

Apparent depth and virtual image position

Why does the virtual image appear right on top of the object and not a little to the right, for example? Is it explained by some formula or just symmetry of the geometry?
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2answers
46 views

Why does black glass reflect better than white one?

Why does black glass reflect better than white glass? Both of them are glasses, so they reflect light. But why black glass reflects better? See below, shiny black glass.
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1answer
49 views

Spatial coherence of SLED light (width of active region?)

As far as I know, super-luminescent diodes (a.k.a. SLEDs) have a very similar structure to laser diodes, except that the front faces of the active region are tilted to prevent the sort of reflections ...
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1answer
41 views

How do you calculate the focal point location of a circular mirror? [closed]

I'm trying to find the focal point and center of curvature of a concave mirror. Just using the radius for the center doesn't seem to work. I know C = 2f, but I'm not sure how to find f or C, given the ...
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1answer
53 views

Snell's law demonstration

I'm a bit confused about a Snell's law demonstration. I'm reading Communication Systems from W. Tomasi. In the chapter 11, the author applies the Snell's law to θent, and -here comes my problem- he ...
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3answers
51 views

How to improve the visibility of light without increasing the brightness?

I am not sure whether or not this is the right SE site to post this question on but I'm sure someone will inform me of my mistake soon enough if it is wrong. Basically I am an Electronic Engineer and ...
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1answer
54 views

Problem with Beam Splitter Refraction

I made a beam splitter for a simple test, as shown in the images below: This was my expected ray trace: But it instead refracted light like this: Why did the splitter cause light to ...
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2answers
64 views

Does a laser beam have to hit the eyes in order to damage them?

Does a laser beam have to hit the eyes in order to damage them? Or can a persons eyes get damaged by looking at a beam that goes past their eyes (e.g. looking at a laser beam moving inside an ...
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2answers
58 views

Why is wax brighter? [closed]

How can wax be normally darker than paper (absorb more light) but apart of light be lighter (let more light go)?
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1answer
42 views

What are the common points between physical optics and geometric optics? [closed]

I am trying to write a paper about light, I want to discuss the two way of studying light, the physical/wave optics and the geometric/ray optics, but I want to write a general introduction about them, ...
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1answer
53 views

How to propagate a planar e/m field in free space using plane waves?

I read this great answer to this question: Numerical software to manipulate a light beam in its plane wave representation? The main thing that I am trying to clear in my head is the following: ...
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179 views

Wavelength used in manufacturing of integrated circuits (IC)

How is it that the silicon ICs industry can burn ICs of a dozen nanometers using photolytography with UV laser of about 193 nanometers? Since the gates are smaller than the wavelength, for example ...
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1answer
45 views

How we can calculate the elements of the Mueller matrix?

Disregarding coherent wave superposition, any fully polarized, partially polarized, or unpolarized state of light can be represented by a Stokes vector; and any optical element can be represented by a ...
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44 views

Does the anisotropic Fermat eikonal equation predict the extraordinary ray direction given by Poynting vector?

Does the anisotropic Fermat eikonal equation predict the extraordinary ray direction given by Poynting vector?
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2answers
130 views

How we see laser light if it travels in a straight path? [duplicate]

Light travels in straight path, and our eyes detects an object's reflected light then we see the object. So if laser light is going in a straight path, how come we can see laser light?
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2answers
48 views

how to trace light after refraction by a camera lens?

I am a programmer and I am doing a camera simulation, I am stuck in a matter of how to know where arrives every ray of light after traveling through the lens and being refracted. Every point of the ...
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1answer
45 views

Optics: how can I see 180 degree relative phase shift between internally and externally reflected light?

Guys this is an example from chapter 4.3 of Hecht's Optics. Top picture shows a light beam moving through a glass medium The second picture shows that when the glass medium is cut into two halves ...
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32 views

faraday's rotation for revealing hidden text

I'm trying to come up with a twist on the known faraday's rotation experiment involving a laser projecting into a polarizer. the polarized light then passes in a selenoid containing a glass rod. the ...
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27 views

Images formed by concave mirror of objects placed between center and focus do not end up as expected

I am more involved with mechanics at this moment, but my sister in 7th grade pointed out that when objects placed in between center and focus of a concave mirror are 'too big' the simple two ray ...
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1answer
22 views

No restoring force in atoms of gas of free electrons (as we have in the upper atmosphere)

While reading about the dependence of wavelength on refractive index, we assume an atom model where atoms stick to their mean position and they are disturbed by the applied electric field causing a ...
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When does a monochromatic beam of light on a reflective surface get completely transmitted?

My book says when when a monochromatic beam of light is normally incident on reflective surface it gets completely transmitted. I am bit confused could you explain me?