# Questions tagged [geometric-optics]

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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### How to calculate the amount of diopters to shift focused point closer to an eye?

In case a human eye has "good enough" focused objects in 1.5 meters and when getting closer, the quality of image loses, how to calculate the amount of diopters to get focused picture (let's ...
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### How to calculate the amount of diopters needed to get focused point closer to an eye?

As far as I know a human eye has approximately 19 diopters and this could be used to calculate the focal point when the observed object is placed in infinity and incoming lights are parallel. How can ...
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### How will Newton's rings look using a Concave-convex lens?

I want to examine lenses that are concave-convex (one for each side) using the Newton's rings method. I'm trying to build the theoretical model for this, but I'm quite sure that the rays of light will ...
1 vote
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### Calculating mirror size for a teleprompter

I'm trying to calculate the required size of a mirror for a teleprompter application. The goal is to use the smallest possible mirror while still capturing the full image. It's a straightforward setup,...
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### How to use ray transfer matrices for practical purposes?

I am familiar with the concept of a ray transfer matrix (ABCD matrix) and how it describes the transformation of a ray with height and angle $\pmatrix{x_0 \ \theta_0}$ into a ray with height and angle ...
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### Direction of propagation of extraordinary wave inside a birefringent medium

I am reading Optics by Ajoy Ghatak, in which the author explains the phenomenon of double refraction in a calcite crystal using Huygens' principle. My query is in the analysis of the case of normal ...
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1 vote
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### 3x3 beam transfer matrix tilt angle transformation [closed]

I'm trying to use the formalism from 'Generalized beam matrices. III. Application to diffraction analysis' and 'Generalized beam matrices: Gaussian beam propagation in misaligned complex optical ...
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### Why aren't all objects and their images same in size?

Suppose there is an object in front of a convex lens and we know that the light rays from each point on the surface of object will converge at a different point and form an image. So that means that ...
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### Directionality of laser light in vacuum [duplicate]

It is well-known that laser light is directional because of coherence from stimulated emission. This means that the light is emitted ONLY in the direction of propagation, and not in any type of ...
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### Eye Floaters Optics

Eye floaters are these annoying objects floating in someones eye, usually seen by someone experiencing them as squiggly lines and dots buzzing around, either dark or partially transparent (I ...
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### What does the optical Hamiltonian mean?

So I was trying to demonstrate Snell's law with Hamilton's equations, and when I got the Hamiltonian: $$H = -\sqrt{n^2-p_{1}^2-p_{2}^2}.$$ I had a question about what this Hamiltonian indicates. I ...
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### Using multiple sources in Zemax mixed mode

In Ansys Zemax OpticStudio [I'm using 2023 R1.00 Pro (11)] sequential mode, the Multi-Configuration Editor can be used to make multiple paths for rays to trace through after the rays depart from a ...
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### Intuitively understanding virtual images in a multi-(thin)lens system

Let's say there is a multi-lens system of a converging lens (ex. a biconvex) and then a diverging lens with an object on the left of the system. And furthermore, let's say that due to the specific ...
1 vote
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### Is there ways to find the most efficient geometrical structure for sunlight concentration? [closed]

we are researching for the most efficient geometrical structure of a concentrator. What we mean by 'most efficient' is that we are trying to get the most sunlight while sun is up. We are not trying to ...
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1 vote
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### Connect gaussian beam waist to ABDC matrix coefficient in bow-tie cavity

As part of my master thesis, my task is to find the optimal parameters to set-up a bow-tie optical parametric oscillator (OPO) for squeezed states generation. I'm currently looking at the possible ...
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### How to Calculate Focal Length when in another medium?

How do you calculate the focal length of a lens when it is placed into another medium, if I only have the focal length of a lens in the air? I understand that the lensmaker's equation should be used, ...
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### What exactly happens to a light ray that is incident on the vertex of 2 mirrors inclined at some angle

So the question I had was that if we have two mirrors as shown in the diagram, what exactly occurs to the light ray that is incident on the vertex of the mirror? If we would like to construct the ...
1 vote
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### How to determine if an observer can see an object with multiple mirrors?

How do I determine if an observer can see an object with multiple mirrors? I came across this image online and I am wondering if the observer (point O) see the object (point A) My attempt: I tried ...
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### What is the apparent location of a real image formed by a lens? [duplicate]

Let's say I place a tennis ball 1 m in front of a plane mirror. The mirror will form a virtual image of the tennis ball, and if I look in the mirror, it appears to me that there is a tennis ball ...
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1 vote
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### Best High Zoom Lens Configurations [closed]

Just wondering which lens configurations are usually best or most optimal for achieving high zoom in the smallest space or with fewest lenses. E.g Let's say we want to achieve a 1000x magnification. ...
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### What is a convex-concave lens?

I came across this term while studying for optics, and I'm unsure as to what this means. My thinking is that it might be a meniscus lens, but the text separately give two different models for each ...
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### How does the mirror know what’s behind the paper?

I found this on social media. Although it was posted for fun, this is a valid question: How does the mirror know what’s behind the paper? Show me how light reflected from the egg reaches the mirror.
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### Spherical aberration of lens

Why is spherical aberration absent in an image formed by a plano-convex lens on its principal axis? Will it be present in other types of lenses?
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### Can the physics behind AR glasses be entirely modeled by geometric optics?

If I wanted to get the image of a small LED screen to be reflected onto the lens of a pair of glasses, would an understanding of geometric optics be sufficient to model this scenario? I ask this ...
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### Behaviour of light in non-Newtonian fluids

So if a ray of light is passed through a cuboidal glass tub, and refraction occurs for the first time and if force is applied on the the fluid laterally, the viscosity would vary and so would it's ...
1 vote
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### Why total reflection happens at only 1 angle?

The critical angle can be intuitively understood by Snell's law.If the incident medium has a bigger diffraction index than the refracted medium then according to Snell's law the refracted ray will be ...
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### How do parallel reflected rays meet to form image at infinity? If they never meet then how is image formed?

In my textbooks it is written that when an object is kept at focus, its image is formed at infinity and is real. But how is this possible because parallel lines never meet and it is necessary for rays ...
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### Lens maker’s formula from parabolic approximation

I’m attempting to derive the lens maker’s formula for a thin or thick lens using the parabolic approximation. I’m familiar with the other proof using the law of refraction and different angles. The ...
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### Formula for power of a lens submerged in a medium

I was always of the opinion that the power of a lens would invariably be the reciprocal of its focal length, irrespective of the medium surrounding it. However, I ran into a slightly different formula ...
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### Is there a way to determine whether what I see is a source of light, a real image, or a virtual image?

Let's suppose you are in a dark room and see something resembling a firefly. The light it emits is so dim that nothing else is visible. You're told that it's either a real source of light or an image ...
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### Is there a way to calculate the angle between the refracted and reflected rays given the refractive index?

Is there a way to calculate the refracted and reflected rays? I know we use Snell's law to calculate the refracted rays, but is there a formula to calculate the angle of the reflected rays, or does it ...
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### Apparent position of object in bowl of water

Say you have a bowl of water and you keep an object in it. What would the apparent position of an object inside the bowl from the position of an outside observer? Will the curvature of the spherical ...
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### Difference between deviation of ray and wavefront

This is a reference to the question posted by Govind Prajapat Refraction of light through a slab of variable refractive index A monochromatic light wave is incident normally on a glass slab of ...
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1 vote
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### Applying Fermat's principle in Fraunhofer's diffraction

The following set up with a source, 2 convex lenses, a slit and a screen is of that of Fraunhofer's diffraction: *Correction S is not on the common optical axis, but above it. $\theta$ = Angle ...
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### Siemens Star Target with black ring - What's causing it?

I am designing an imaging system with should create an image from focal plane to focal plane (in contrast to infinity to focal plane). The system features a lens with tunable focal length. Starting ...
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### Why do the solutions to the parabola in Bessel's formula gives the distances where sharp image is formed?

I had an optics lab in the previous week where we tried to measure the focal length of a lens using Bessel's method. My question is about this method. So, in order to obtain Bessel's formula we do the ...
1 vote
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### How to determine the light rays difference according to book by Okamoto?

In the very beginning of the book "Fundamentals of Optical Waveguides" by Okamoto, there is a description of light ray propagation in the waveguide. I provided an updated Figure from it: ...
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### Finding magnification of microscope from focal lengths

How do you find the magnification of a microscope given the focal lengths of the objective and eyepiece? What else can you find given this information? If finding the magnification is not feasible ...
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### Can a real object also be considered as a real image if the direction of rays were to be reversed?

I came across the concept in a book wherein a real object is classified as a body that emits diverging beams of light; whereas the virtual objects are a point or a collection of point where the light ...
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### Does the beam image invert on each round-trip through a hemispherical laser cavity?

When one creates a hemispherical laser cavity, using one flat and one concave mirror, does the beam image invert each time it makes a round trip? I know when passing through the focus of a lens/mirror,...
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### Mathematical definition of ray

I have just begun studying geometrical optics, and there is something mysterious about it. What I want to know is how to derive the definition of ray from Maxwell's equation. In vacuum, ...
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### Finding the limiting refractive index of a rainbow

Give the limiting refractive index of a rainbow. The raindrops are modelled as spherical droplets, with refractive index $n$, with parallel rays from the Sun incident on it. I have a very limited ...
1 vote
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### What would I observe with a light microscope operating at its full magnification if the specimen was smaller in diameter than the used wavelength?

Would I still see the specimen but completely blurry? or wouldn't I see it at all? For example, let's say the wavelength of the light used is 600nm and the diameter of the specimen is 550nm.
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### Object and Image Distance from Image height, Object height, and focal length [closed]

Is there a way to find the object and image distances from the object height, image height, and focal length? I understand that the magnification is equal to $-\frac{d_i}{d_o}$ or $\frac{h_i}{h_o}$, ...
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### How is a complete image of a distant object formed with an obstruction in the line of sight? [duplicate]

Can anyone please link to or sketch a diagram demonstrating how a complete (and clear) image can be formed of a distant celestial object with a central obstruction blocking part of the line of sight ...
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### How do you derive the formula's for equivalent focal length and back principle plane for 2 thin lenses separated by a distance?

I've found online that the formula for the effective focal length of 2 lenses separated by a distance is: $$\frac 1f=\frac 1{f_1}+\frac 1{f_2}-\frac d{f_1f_2}.$$ However, I'd like to know how this ...
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### Input Parameter Location for 3x3 Beam Trace Matrix for Misaligned Optical System

I'm trying to use a 3x3 beam transfer matrix from "Generalized Beam Matrices: Gaussian Beam Propagation in Misaligned Complex Optical Systems" by Anthony A. Tovar and Lee W. Casperson https:...
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### Multiple lens configuration thickness and distances

Struggling to understand where I should measure lens thickness and distance between lenses from. I've attached an example multiple lens setup. For determining individual lenses thickness is it simply ...