Tagged Questions
0
votes
0answers
14 views
Problem in angle measurement [migrated]
From the above picture we can prove easily $ CF = XF$ because CFX is a isosceles triangle. Now if we move the point X more near near P, it will give the same results(I mean we will get again $ CF = ...
0
votes
0answers
43 views
Is my textbook in error about this geometric optics relation?
Given a centered optical system (having an axis of rotational symmetry), let $H_1$ be the intersection of the optical axis and the "principal object plane" (I'm studying in French and have no idea how ...
1
vote
2answers
160 views
Light Ray Reflection from concave mirror
Suppose a ray of light hits a concave mirror and is parallel to principle axis but far away from it such that it doesn't follow paraxial ray approximation. Will it pass through focus or between focus ...
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 ...
1
vote
1answer
86 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 ...
0
votes
2answers
98 views
Can virtual image be photographed
Is there any instrument that can photograph the virtal image and by what principle it is working on ? ?
1
vote
2answers
99 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 ...
0
votes
1answer
63 views
Which fraction of light is refracted from a source of light under a lake?
I was trying to solve this problem:
"A punctiform source of light is standing inside a lake, at a height h of the surface. f is the fraction of the total of energy emitted that escapes directly from ...
0
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0answers
9 views
Image formation [duplicate]
What is the real cause behind the formation of an image? It is explained as" when rays of light focus at a point image is formed." So here we have two events, one focusing of light and another ...
1
vote
2answers
75 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
1answer
86 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 ...
14
votes
2answers
392 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. ...
4
votes
1answer
128 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 ...
1
vote
1answer
155 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 ...
4
votes
2answers
180 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 ...
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 ...
6
votes
2answers
135 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 ...
3
votes
1answer
258 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
2answers
167 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
2answers
301 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 ...
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 ...
0
votes
1answer
183 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 ...
0
votes
1answer
244 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 $b$?
1
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0answers
142 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 ...
6
votes
0answers
181 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 ...
0
votes
1answer
118 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 ...
2
votes
1answer
146 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
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 ...
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
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 ...
2
votes
3answers
221 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 ...
1
vote
0answers
330 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 ...
2
votes
0answers
63 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 ...
2
votes
1answer
239 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 ...
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). ...
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
3answers
428 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
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 ...
3
votes
1answer
229 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 ...
1
vote
1answer
482 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 ...
2
votes
3answers
840 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?
6
votes
2answers
456 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 ...
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)
...
15
votes
3answers
31k 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 ...
3
votes
3answers
3k views
How do contact lenses work?
I understand how telescope, microscope and glasses work.
But how do contact lenses work?
7
votes
8answers
910 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 ...
