The subfield of optics in which light propagation is approximated in terms of rays. It mainly includes reflection and refraction on surfaces.
131
votes
14answers
41k 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?
15
votes
3answers
30k 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 ...
14
votes
2answers
389 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. ...
7
votes
8answers
902 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 ...
7
votes
2answers
694 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 ...
7
votes
2answers
62 views
Is light red shifted in optical tweezers?
This is a question I put to my supervisor during my PhD many years ago, and never really got a satisfactory answer to.
In an optical tweezers, assume that a beam of light is used to move a glass ...
6
votes
2answers
452 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 ...
6
votes
2answers
133 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 ...
6
votes
0answers
178 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 ...
5
votes
2answers
308 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 ...
4
votes
5answers
303 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 sendt in at some angle. Will it always eventually exit through ...
4
votes
2answers
179 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 ...
4
votes
2answers
3k 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)
...
4
votes
2answers
2k 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 ...
4
votes
1answer
139 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 ...
4
votes
3answers
426 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 ...
4
votes
2answers
1k 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). ...
4
votes
1answer
127 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 ...
3
votes
3answers
2k 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 ...
3
votes
1answer
135 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?
3
votes
2answers
289 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 ...
3
votes
1answer
243 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, ...
3
votes
3answers
454 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 ...
3
votes
3answers
3k views
How do contact lenses work?
I understand how telescope, microscope and glasses work.
But how do contact lenses work?
3
votes
2answers
162 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 ...
3
votes
1answer
228 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 ...
2
votes
3answers
220 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 ...
2
votes
2answers
139 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 ...
2
votes
3answers
2k 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 ...
2
votes
3answers
821 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?
2
votes
3answers
109 views
What does it mean that a wavevector is null?
I have derived geometric optics for gravitational waves and I am trying to interpret one of the results. I have
\begin{equation}
k_{\rho}k^{\rho}=0
\end{equation}
for the wavevector. For the case ...
2
votes
1answer
235 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 ...
2
votes
1answer
145 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 ...
2
votes
2answers
63 views
Proof that a spherical lens is stigmatic
In geometric optics, we generally allow that, for example in the case of a convex lens, rays coming from a particular point get refracted towards another particular point on the opposite side of the ...
2
votes
0answers
62 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 ...
1
vote
2answers
97 views
Why don't you see multiple images of an object?
Consider the ray model of light. Let's say an object such as a pencil is illuminated, and consider one point on that pencil. Since there could be many rays of light bouncing off the same point on the ...
1
vote
1answer
143 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 ...
1
vote
1answer
477 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 ...
1
vote
1answer
79 views
Why can't we see real images?
When light from an object passes through a convex lense, it gets reconverged at a single real image. From there, the light rays presumabely begin diverging again, exactly as if there was a ...
1
vote
2answers
88 views
How does the eye perceive a real image?
Okay, so I'm trying to grasp how the human eye will perceive the real image created for example by a convex lens. Take the upper image in this picture for example.
If you were to place a screen at ...
1
vote
1answer
80 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 ...
1
vote
1answer
149 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 ...
1
vote
1answer
89 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 ...
1
vote
2answers
170 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 ...
1
vote
2answers
122 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 ...
1
vote
2answers
74 views
All mirrors always shrink to 50% scale?
I have this geometric optics exercise here, in which a man is looking at himself in a mirror.
Determine the minimum height at which the bottom of the mirror must be placed so the man can see his ...
1
vote
0answers
138 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 ...
1
vote
0answers
324 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 ...
0
votes
2answers
89 views
Can virtual image be photographed
Is there any instrument that can photograph the virtal image and by what principle it is working on ? ?
0
votes
1answer
98 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 ...
