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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Huygen's principle and why can't we see atoms with light

First of all, I'd like to discuss Huygen's principle. In order to explain waves diffraction, it says that every point in a wave front behaves as a source, so the next wave front is the sum of all ...
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74 views

Do we have a deeper understanding of Fermat's Principle?

Fermat's principle says that light travels between two points along the path that requires least time as compared to other nearby paths. But why this is so? Why can't light follow other paths? How ...
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14 views

Poisson Spot vs. Shadows

In textbooks, whenever I read about the Poisson spot, it involves a disk, and having light waves diffract around it and interfere constructively in the center. At the same time, when I read about ...
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29 views

Question about reflecting telescope

In a reflecting telescopes, light is reflected from a primary concave mirror to a secondary mirror. But the secondary mirror is never placed at the focal point of the primary mirror. Why is that? ...
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19 views

Electromagnetic transfer function

In a paper on the superlens, I came across the term of "transfer function". I understand that the transfer function relates the output to a given input, but I've been unable to find a formula for the ...
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44 views

Does Silver posses a color or Is it colorless reflection? [duplicate]

Why is silver said to have a color whereas water is not? Water is colorless because is allows penetration of light and doesn't reflect a colored wavelength, whereas Silver reflects light from its ...
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46 views

Problem on Malus law? doesnt work on certain angles [closed]

if Unpolarized Light falls on two polarizing sheets placed one on top of other. what must be the angle between the characteristics directions of the sheet a) if the intensity of the ...
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18 views

Get actual object size in mm using camera [closed]

How to get actual object size in mm when we know Object distance, focal length, image width in pixels and camera angle,
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22 views

Recommended books that describe emission and absorption of light and light/matter interactions

Hello I am a Chemical Engineer that has ventured into the field of optics and I was wondering if there is any recommended book/books to understand the maths and also some answered exercises or ...
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22 views

curvature tensor

I'm reading Tailored freeform optical surfaces, and having trouble in understanding it. Setting: A ray from a source $\mathbf{s}$ aimed at a point $\mathbf{p}$ on the optical surface, the ...
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31 views

Why we see a distant object more closer from us with a telescope?

The side magnification in the image obtained by a telescope its always less than 1, then, Why we see a distant object more closer from us?
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1answer
49 views

Is a non reflective display possible?

Can you think of a surface, that emits light, but doesn't reflect any light coming from outside (absorbs it)? Under what circumstances would this work?
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1answer
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In a lens the image formed by the first surface serves as the object for the second surface.What is the reason?

When deriving the lens maker's equation I faced the problem of understanding the logic behind this reasoning "image formed by the first surface of a lens serves as the object for the second surface."
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37 views

Determining path of light through a nanolens

In the case of light passing through stacked liquids, we can use a ray approximation of the path of light to determine the path taken through each layer of liquid using Snell's law. From all the ...
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14 views

Optimal wavelength for low IR attenuation under normal atmospheric conditions?

I can't find any good data about the transmit attenuation of infrared light in the atmosphere transmitted horizontally (there is a bunch of stuff detailing penetration of radiation from space, but ...
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0answers
25 views

How much UV light do we have on the ground? [closed]

We cannot see it. But suppose each UV photon is replaced by a red light photon, does it make the world look as bright as it is just before the sunrise?
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1answer
111 views

Why do we use the index of refraction for yellow light?

When we do problems with optics and refraction, we’re usually given a set of indices of refraction to work with; for example, the index of refraction in air is about 1.00, the index of refraction in ...
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54 views

Re-reflecting in HUD optics

Simple HUD optics design can be described with below image. (source : http://www.mikesflightdeck.com/hud/head_up_displays.html) As you can see, if combiner and colimating lens(after fold mirror) ...
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1answer
54 views

Do parallel rays reflecting at a mirror not intersect at one point? [closed]

Let's take a concave mirror with $CP$ as its principal axis. Let's assume that a parallel ray $p$ to $CP$ reflects at $A$ to pass through the focal point $F$. Then, $\angle CAF=\angle ACF$, which ...
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1answer
46 views

Brightness of light sources

I would like to know what determines the brightness of light.I'm confused,After hours of reading i got these definitions mixed up i need to link them together : Light intensity Brightness of light ...
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3answers
47 views

Green light on red article

When white light falls on an object the body absorbs all colors of light and reflects some colors of light which we see the object to be.For eg.A red ball reflects red color and absorbs the rest ...
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1answer
20 views

Which features effect on the Reflection of things?

I'm working on something and I need to find a wire that doesn't reflect well. so, I know one feature is the color of the wire to decrease the reflection. But what other features effect on the ...
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33 views

Why does being unable to collect all emitted light from a source lead to the diffraction limit?

My optics textbook (Hecht & Zajac) says the following: Most commonly, the function of an optical device is to collect and reshape a portion of the incident wavefront, often with the ultimate ...
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1answer
59 views

What operation does a beam splitter apply?

What is the unitary matrix equivalent to the operation of a beam splitter? I'm asking because I've seen different matrices used and was wondering if the term is just ambiguous or if there's an agreed ...
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28 views

Why does not the optical fiber break? [duplicate]

Glass is a very fragile object. So why does not the optical fiber break? Everytime I take them, I am worried about this problem.
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1answer
62 views

How can we see objects that are so far away? [duplicate]

The HUDF used to be the deepest image of the universe ever taken by the Hubble telescope, the furthest star in this image is 59000 light years away. The star in question: Now Imagine a light ...
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False sunset and false sunrise time estimation

False sunset and false sunrise are described . Here is a sample day rise and set time according to AccuWheather site and calculated value of sunrise and sunset in my country. Could you please help ...
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Is it possible to calculate the relative abundances of elements in the sun based on its line spectrum using a common lab spectroscope?

There are many problems that I feel would hinder the process: atmospheric noise, light pollution etc. Let's assume that I bypass these problems and get an accurate emission line spectrum on the ...
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1answer
73 views

How to extract depth of a pixel from an image?

I'll have a few pictures that show the same scene, but only a few things move around a little bit. Now I don't have an information about any size in real life but I'd like to extract a scaling factor ...
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How to measure the wavelength of a laser pointer?

I'm working on something and I need to know the wavelength of the laser pointer that I'm using. Can you suggest me a way, using some optics formulae, or anything else to calculate the wavelength?
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1answer
38 views

Is crystal diffraction actually diffraction?

It seems like a very common model that is taught in schools for crystal diffraction is that there is an incident plane wave of light on a crystal lattice, and each atom in the lattice scatters the ...
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Why is a time-varying phase equivalent to a spectral shear?

A spectral shear of an optical pulse can be achieved by inserting a time-varying electro-opto (EO) crystal in the beam path to modulate the phase of the pulse. How is this spectral shear achieved ...
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25 views

Optics Spatial Resolution

what does it mean to have a micrometer spatial resolution. Does it mean the resolution is 1 micrometer or can be 2,3,4,.... etc.? I do not understand it. Is there anybody?
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334 views

Why are non-linear optics called non-linear?

Looking at the wikipedia article on nonlinear optics you can see a huge list of frequency mixing (or multi-photon) processes. What makes these different from single-photon interactions? More ...
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1answer
80 views

How do solar cells increase the lifespan of the Sun?

While reading "Physics of Solar Cells" by Würfel, I came across an amusing statement: An interesting aspect arises if we had to pay for solar energy, but could also get a refund for energy ...
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Coordinate Transformation across different media

I have an arrangement that is as follows : (1) inner cylinder(radius r1) filled with water (2) outer cylinder(concentric, radius r2>r1) made of glass I have a sensor S1 at radius r(r1) at angle beta. ...
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39 views

Is there a formula to calculate the deviated angle of a ray passing through a prism?

I'm assuming the angle of incidence to be the number of degrees from a perpendicular line on the side of a prism the ray starts passing through... I'm trying to figure out the angle the ray would be ...
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1answer
64 views

Why isn't this calculation of the energy of a light wave correct? [closed]

I'm trying to calculate the energy $J(T)$ that monochromatic light wave with electric field strength $E(T)$ supplies to unit electric charge over period of time $T$: $J(T)=\int\limits ...
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15 views

Interference on curved film

Let's say I have a curved film in the XY plane, delimited by $y=0$, $y=\sqrt{x}$, $x=L$. Now I light the thin film from the top and I try to see the interference pattern by transmision. I'm stuck ...
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The optics of vortex (in water): why there is a bright ring?

This picture is from this YouTube video from "Physics Girl", which shows how you can generate vortices in a swimming pool by using a plate: And there she explains the creation of the shaded circle ...
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2answers
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Using a transfer matrix to calculate beam width of off-axis Gaussian beam?

I have been reading a lot about ABCD matrices that are used for ray tracing. I can calculate the output offset $r_{o}$ (with respect to the optical axis) and the angle $\theta$ of the ray by $$ ...
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What causes this pattern in the reflection of a laser on a screen? [duplicate]

When I shine a red laser behind me at a wall I see a strange reflection occurring on my laptop screen Why does this happen? The pattern on my screen occurs exactly where the laser is hitting the wall. ...
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1answer
35 views

How do I determine lens placement inside the minimum focus distance?

I've seen this solution which explains how head mounted displays work but I need to know where to place the lens. The previous solution used an objective lens to focus collimated light, I'm assuming ...
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100 views

Why do sea waves seem to be standing still when you look from the window of an airplane?

Looking from the window of a passenger plane even at moderate altitude such that one can still recognize individual waves and even something like white foam, and small boats close to the cost line, it ...
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42 views

Resolution of two frequencies

If I am trying to resolve two features in frequency space, with central frequencies A and B and a 'spread' (standard deviation, FWHM etc.) of $\sigma_A$ and $\sigma_B$ what is the spectral separation ...
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3answers
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images of objects at infinity

Is the focal point of our eye lens is on the retina? if it is so why dont we see point image of infinite object because light rays coming from them are parallel to each other and converges at focal ...
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3D glasses and reflection/polarisation [duplicate]

Hi all, Tonight I'm going to see a 3D film so I thought I'd check whether I had any old 3D glasses around the house. Found a pair of "RealD" glasses. Anyhow, I assume that the glasses use some ...
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1answer
30 views

Gaussian beam shape

In this diagram of a Gaussian beam, why does the radius vary with z position? Is it assumed that a Gaussian beam is always being focus by a lense? Why can the beam not go any smaller than $w_0$ and ...
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1answer
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A Difficulty with Liquid Metal Mirror Telescopes

"Another difficulty is that a liquid metal mirror can only be used in zenith telescopes" [Wiki] Why is that? Why can't a series of flat mirrors be used to reflect light coming from any angle to be ...
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Asymmetric photoluminescence spectra

Why do photoluminescence spectra have asymmetric lineshapes as those here http://www.scielo.br/img/revistas/bjp/v37n4/a04fig01.gif or here: ...