The subfield of optics in which light propagation is approximated in terms of rays. It mainly includes reflection and refraction on surfaces.

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280 views

Eikonal approximation for wave optics. Why follow the unit vector parallel to the Pointing vector?

The description of the passage from wave optics to geometrical optics claims that light rays are the integral curves of a certain vector field (the Pointing vector direction, normalized to 1). Here ...
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2answers
651 views

Can't seem to reconcile geometric optics and wave optics

I was looking at a physics situation involving light, and I can make the correct derivation assuming light is a ray of a given intensity (geometric optics), energy conservation checks out, everything. ...
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2answers
1k views

Does light reflect if incident at exactly the critical angle?

A lot of textbooks and exam boards claim that light incident at exactly the critical angle is transmitted along the media boundary (i.e. at right-angles to the normal), but this seems to violate the ...
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1answer
191 views

On the optics of high-resolution surveillance drones

In this youtube video (which is an except from a documentation I believe) a DARPA development for a high-resolution surveillance camera is presented. This question is regarding the optics that are ...
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1answer
286 views

Thin lens formulae

Hi I have a question about applying the thin lens formula $$ \frac{n_1}{s_o} + \frac{n_2}{s_i} = \frac{n_2 - n_1}{R} \,\text{thin lens formula}$$ for a single lens emerged in medium $n_2$ in the ...
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2answers
408 views

Goldfish perspective

What does the world look like from the Goldfish point of view, from inside a spherical aquarium? If our eyes were inside, would we be able to see the straight lines, focus on different objects and ...
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1answer
283 views

Correcting for bad eyesight on display monitors [duplicate]

I think it would be neat if one could configure one's eyesight parameters (astigmatism and myopia in my case), viewing distance, and perhaps age into a special display driver, such that a computer ...
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2answers
255 views

Why does a blue sky at dusk appear nearly black through a telescope?

Earlier this evening I was looking at the Moon through my cheap toy telescope (x150 magnification) when I noticed a (rather mundane) optical effect I couldn't explain. The Sun had just dipped below ...
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1answer
927 views

Beam splitters- Direction of use

There are two cases I'm asking about. The square in the middle is a cube beam splitter in the same orientation for both cases. We are looking at the beam splitter from the top. In the first case, ...
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2answers
278 views

Redirecting light beams from beam splitters

I'm doing a project where I am taking a laser beam and sending it through a beam splitter. As I understand, approximately 50% of the light will go pass through and 50% will be reflected. So this means ...
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1k views

How to make the projected image smaller by adding one ore more lenses in front of the built in projector lense?

I have a projector that creates a large image, even if the distance to the screen is short. The device is very small, approximateley 10x10 cm if you look from above. The height is only 3 cm. I ...
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1answer
149 views

Why a star commonly exhibits 6 rays?

Have you realized, that often the photo of a star shows 6 rays spreaded symmetrically around it, independently of the camera chosen? Do you have idea of what kind of optical phenomena is behind it?
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1answer
142 views

Optical waveguide that can displace a 4D light field

Has anyone invented an optical waveguide that can "pipe" a scene from one place to another unaltered? More precisely, I want to displace (and/or rotate) a 4D light field. An optical waveguide is an ...
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1answer
335 views

If light diverges, how can there be a virtual image?

I have seen this question: Why can you see virtual images? but answers evade the question. Light needs to hit the retina in order, what is the meaning of "dashed" lines in most visualizations that ...
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2answers
224 views

How did ancient physicists around 500 BC decide that the earth is spherical?

One of the standard stories that is given for this (and is mentioned in Aristotle) is that the hull of a ship disappears first as it sails towards the horizon on a calm sunny day. Is this a myth, or ...
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2answers
387 views

How much of himself a person can see in the mirror? [closed]

A man who is $6$ ft tall is standing in front of a plane mirror that is $2$ ft in length. The mirror is placed lengthwise with its bottom edge $4$ ft above the floor on a wall that is $5$ ft ...
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1answer
476 views

How does the Fraunhofer irradiance distribution look for a double slit aperture of different lengths?

How does the Fraunhofer irradiance distribution look for a double slit aperture with $d$ = integer multiples of $b$?
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0answers
284 views

What are Jones matrices and how to derive them?

I'm coding a software for an optics lab I'm working in and I need to know how to derive expressions for Jones matrices for various polarizes. What does a Jones matrix represent and how would you ...
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1answer
348 views

light ray 'entropy'

Is there something like an entropy law for light rays? I came up with the following experiment: A black box has two circular holes in it, a small and a large one. I don't care about there ...
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1answer
222 views

How to define the required aspherical coefficients for a lens?

I would like to purchase my own aspherical lens for testing purpose. Then I need to define the required coefficients. But how? My known requirements are f=25mm F/# 2.0 and MTF 0.5 @ 120lp/mm with a wl ...
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1answer
225 views

Curved lines in a picture (Photography)

My problem is when I take a picture (a close one) the straight edge looks a little curved. In a standard camera, like a CyberShot. I would like to know if there is some relationship between the ...
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3answers
5k views

Clarification needed in the concept of apparent depth & real depth

I understood the concept of apparent depth from here: But one thing I didn't understand is, will there be difference in the real depth and apparent depth when we are looking not at an angle as ...
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1answer
223 views

Is there a known optical design for a beam compressor?

With my little knowledge of optics I have come across some 'known' designs such as the Double Gauss for example, is there a 'beam compressor'. My requirements are to reduce an incoming parallel ...
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2answers
179 views

Intensity loss due to vignetting

I was trying to get an expression for the loss of intensity due to vignetting in a simple optical system, and got a fairly complex integral. I was wondering if there's an easier way, or any book that ...
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3answers
278 views

mirror house gedanken experiment

Imagine a mirror house i.e. completely made of mirror with no traces of whatsoever light absorbent. Now, you introduce a light beam into that room and observe somehow through a hole. Would the room ...
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0answers
588 views

How to use the Coddington shape factor?

We are given $\sigma=\frac{r2+r1}{r2-r1}$, with $\sigma$ being the Coddington shape factor. What I am having problems with is solving for $r1$ and $r2$ when I am just given a focal length and a ...
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0answers
80 views

Optics: finding total power of a syste, including wavelength

Specifically I need to create an ABCD matrix given 2 radii of curvatures, the thickness of the lens, type of glass (BK7) and a given wavelength. I will have to figure this out eventually, so help ...
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1answer
342 views

Plenoptic camera and display

This is a two part question about the technology described here: Lytro's light field camera lets you choose focus later I'd love to get an explanation of the technology. What is the ...
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2answers
2k views

How to find the principal point in an image?

I need to find the principal point in an image. Its a point where the principal axis intersects the image sensor. Due to misalignment this point is not at the center of image always(or image sensor). ...
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2answers
346 views

How to place a mirror parallel to a wall?

For one of my experimental setup I need to place a mirror perfectly parallel to a wall. It can be placed at any distance from the wall. I would like to use any method other than direct measurement. I ...
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3answers
610 views

Virtual images in (plane) mirrors?

The following image is taken from teaching physics lecture Was man aus virtuellen Bildern lernen kann (in German): Now the cited paper claims that the left hand side is the correct picture to ...
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5answers
390 views

Trapping a lightray

Given a solid whose interior is a hollow sphere with perfectly reflecting mirrors. A small hole is drilled in the sphere and a photon is sent in at some angle. Will it always eventually exit through ...
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17answers
58k views

A mirror flips left and right, but not up and down

Why is it that when you look in the mirror left and right directions appear flipped, but not the up and down?
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1answer
284 views

Which lens parameters determines it's format?

I'm working with a megapixel sensor with a 1/2" format. I would like to know which parameters have to be taken into account in order to design a lens that can be fit with 1/2" format. The light ...
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1answer
664 views

Can reading glasses improve one's eyesight of objects lying in the long range?

Someone told me that reading glasses (a priori with a magnifying glass effect only) improve one's eyesight of objects lying in the long range distance. I am really sceptic about it since everything is ...
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3answers
2k views

Why should optical fibers be thin?

What are the reasons that optical fibers have to be thin (small radius of the fiber)? Is there a good picture which explains this in detail?
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3answers
4k views

Cladding of optical fibers

Why do optical fibers usually have a cladding? Ok, if you put make a bundle of optical fibers this prevents that light leaks from one fiber to another fiber in contact. However, are there other ...
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2answers
3k views

Software for geometrical optics

Is there any good software for construction optical path's in geometrical optics. More specifically I want features like: draw $k \in \mathbb{N}$ objects $K_1,\dots,K_n$ with indices of refraction ...
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3answers
575 views

Snell's law starting from qft? [duplicate]

Can one "interpret" Snell's law in terms of QED and the photon picture? How would one justifiy this interpretation with some degree of mathematical rigour? At the end I would like to have a direct ...
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2answers
880 views

Do all light rays from a point passing through a thin lens converge at the image?

I have often seen diagrams, like this one on Wikipedia for a thin convex lens that show three lines from a point on the object converging at the image. Do all the other lines from that point on the ...
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2answers
7k views

Why do things that are far away seem smaller?

As you see things that are far smaller, a funny question about this: Imagine there are many people in a row (all are same height) ...
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2answers
875 views

Can you shake your reflection's hand?

For a spherical mirror, an object at the mirror's center has an image that is also at the center. Its magnification is $-1$. For a video showing this, see here. If you stand slightly behind the ...
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3answers
74k views

Virtual vs Real image

I'm doing magnification and lens in class currently, and I really don't get why virtual and real images are called what they are. A virtual image occurs the object is less than the focal length of ...
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3answers
5k views

How do contact lenses work?

I understand how telescope, microscope and glasses work. But how do contact lenses work?
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8answers
2k views

Is it possible to make glasses that make everything brighter, but do not magnify or focus?

Corrective glasses are usually intended to help focus light on your retina. Supposing I had good vision already, but simply wanted more light, could I make glasses that would send more light into my ...