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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Absolute refractive index and power of lens

The power of a lens is the degree by which the lens can bend light, and the absolute refractive index is also the same. What is the difference between them? Is the power of a lens an absolute ...
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Question about a specific geometrical optics/Fermat's principle problem and it's given solution

I'm studying the following question from the book 200 More Puzzling Physics Problems (Gnädig, Honyek, Vigh). The proposed solutions seems a little off to me. The first approach is by Fermat's ...
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Sign convention in refraction at spherical surface

While deriving the formula for refraction at spherical surfaces: $$ \frac{n_{2}}{v}-\frac{n_{1}}{u} = \frac{(n_{2}-n_{1})}{R} $$ We use the sign convention that object distance = -u Then while ...
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How would Newton explain mirages?

Suppose we think of light as photon packets with tiny momentum, then with this picture in mind, go and see the refraction of light in mirages: We see that the packets of light photons must be ...
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What is a rainbow?

What is a rainbow? I've read that an image is formed when light rays after reflection meet. So in case of a rainbow when light ray after refraction by the water droplet reaches our eye than wouldn't ...
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Why does light bend when it enters a medium?

I am asking this question after referring to @benjimin answers at Why does light bend? I found the same answer at wiki. But i found a video on youtube by doctor don (https://www.youtube.com/watch?v=...
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Why doesn’t an irregular or polygon shaped hole work like a pinhole camera when held close to the screen?

When a card with a hole of any shape is held close to the screen, the lighted area on screen is of the same shape as the hole. To make an image of light source, say Sun, the card has to be moved away ...
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How would a rainbow from a divergent light source look like?

Many explanations of the shape of rainbows as constant angle reflections do assume the light, incident on rain droplets, to be a parallel beam of light rays. That might for the sun-earth system be ...
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Lens theory, what sets the angle of view in photography?

Is this correct statement that - in photo equipment angle of view forms from dimensions of sensor i.e. if we draw line from top most and bottom most edge of the sensor trough center of the lens we get ...
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1answer
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Behavior of a laser beam in a spherically symmetric medium [closed]

A laser beam propagates through a spherically symmetric medium. The refractive index varies with the distance from the centre of symmetry $r$ according to the equation: $$ \mu=\mu_0\frac{r}{r_0} $$ ...
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Can we witness Optical illusion in which sun appears to set in mid sea than at horizon?

I was searching for optical illusions and came across a video on youtube where sun seems to set in the mid of sea instead of setting at the horizon? Can anyone please explain how this illusion takes ...
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Magnifying power of water-air surface

If you look at an object through water it looks bigger/closer: I am trying to compute the magnifying power of the water-air interface and got stuck at some point. In particular I want to compute the ...
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Refraction across two interfaces: Snell's laws for a light ray and the law of sines for a triangle

I got intrigued by a paradoxical thought when thinking of light rays that are refracted twice. Polite request: please use answers for answering, and comments for commenting or asking. A light ray ...
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If diverging rays never meet, why do parallel rays meet at infinity?

I've seen that in the case of concave mirrors if the object is between focus and the pole - the reflected rays diverge and never meet. But if the object is at the focus, it's defined to be meeting at ...
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Find the change in height after rotating the mirror

Here's the question directly from the book: Sunlight enters a room at an angle of 32$\circ$ above the horizontal and reflects from a small mirror lying flat on the floor. The reflected light forms a ...
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How do we perceive object distance in refraction/reflection?

Suppose we have some object, from which light rays reflect off and reach our eye. In this example, we can directly see this object, and the image is formed on our retina. However, consider a coin kept ...
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Is this given ray diagram for a biconvex lens correct?

Figure shows a biconvex lens of having radius of curvatures as R1 and R2 , in the ray depicted shouldnt the meeting point of the rays be at 2F and the object should be placed at -2F , where F is the ...
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Refraction across two interfaces: is it correct to use Snell's law as constraint in an application of Fermat's principle?

The problem area is geometric optics, namely refraction across homogeneous media with constant speed of light. I explain the three steps of a methodological doubt that popped up. Polite request: ...
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Mirrors, how can I prove a beam hits at a particular place

I have two mirrors (red segments) that are parallel, that have certain angle alpha with the horizontal line, and when the first mirror with a fixed center rotates it makes the second mirror move so ...
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1answer
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Nitpicking the definition of Angular Magnification, missing info

I have seen angular magnification defined as "angle subtended by image"/"angle subtended by object, but that is very vague. I have seen it defined as the ratio of the tangents of the ...
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Double crystal monochromator geometry

This is more of a geometry question. Here is a first picture showing the dcm (the two crystals in black for a certain angle, and light blue for a smaller angle). The red (and orange) is the laser's ...
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What happens to the intermediate images in Optics?

A common method to solve problems in optics for system of mirrors, surfaces with different refractive index, lens, slabs, mixture of mirror and lens etc. is to consider the image formed by the first ...
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How might I calculate the trajectory/deflection of a light beam near Schwarzschild and Kerr black holes?

Suppose I have a light beam (or a photon), with origin $\mathbf{o}$ and ray direction $\mathbf{d}$, and a Schwarzschild/Kerr black hole at the origin with Schwarzschild radius $r$, such that $||\...
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Which is more accurate, a quantum gyroscope or ring laser gyroscope?

I can't find any source which says whether quantum or laser gyroscopes are more accurate. I'm also wondering what the advantages and disadvantages are of each technology.
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How do I compute a Mueller matrix for a refracted ray?

When I consult most resources, I get a set of equations for Fresnel reflection and transmission which look like this: $$ r_\text{s} = \frac{n_1 \cos \theta_\text{i} - n_2 \cos \theta_\text{t}} ...
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Is rainbow formed in front or behind of a water droplets?

Single water droplet gives rise to formation of only a small part of rainbow. Is that part formed in between observer and droplet or behind the droplet and not between them?
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Why is the number of light rays refracted from a transparent media more than the number of reflected rays?

I came across a question related to the multiple image formation from a thick mirror due to partial refraction and reflection. It was asked that which image would be the most intense? In the solution ...
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Spatial Resolution and pixel smear and camera devices

Can anyone recommend a good source (video, textbook, online course) that I can use to learn more about spatial frequency, exposure, pixel smear, how cameras work. I only have some basic optical ...
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How far away does a taller object have to be in order to appear below eye-level?

A thought experiment between a friend and I. Let's say I'm 6ft tall, and I have a friend who's 7ft tall. To keep things very simple for the sake of discussion, we're on a flat level plane, and I have ...
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1answer
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Intuitive Explanation behind algebraically adding the vertical shifts produced by transparent objects

Given are two transparent slabs of different refractive indexes, a point object is placed at the bottom of $B$. My book says that the total shift produced is the algebraic sum of the shifts of each ...
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1answer
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Optics of Vehicle Convex Mirrors

I recently got in an argument with a friend while I was driving. When I moved to a different lane, I did not turn my head to check for any vehicles in my blind spot. Instead, how I checked was by ...
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Why do the eyes of a person wearing glasses not look blurry if almost everything looks blurry when I wear them?

When I wear my mother's (hyperopic) glasses, almost everything appears blurry, (the reason for which was explained in this answer). What I don't understand, is why this doesn't work backwards. ...
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How can the image be any size orher than the object?

Am image is just the set of images of all the points on the thing. The complete image has to be the same size as the object if there is exactly one image for each point on the object forming it. So an ...
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Proof of Snell's law [duplicate]

Snell's law states that $n_1 \sin i = n_2 \sin r$ where $i$ is the angle of incidence, $r$ is the angle of incidence and the refractive index, $n = \frac{c}{v}$ where $v$ is the velocity of the light ...
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Galilean telescope magnification coefficient?

So I've seen the magnification coefficient of the compound concave telescope to be $\frac{f_0}{f_e}$, but what is the magnification coefficient in the case of the convex galilean telescope? This may ...
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Generation of an beam with an arbitrary initial profile

Is it possible to generate a beam with an arbitrary initial profile? For example, the finite Airy beam has an initial profile $$\phi(s,0)=exp(\alpha s)Ai(s).$$ In practice, this finite Airy beam is ...
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Real or false image formation of a plane mirror and lens [closed]

If an object is placed in-between a plane mirror and a convex lens. Would the image that results from the reflection off the plan mirror into the lens be real. Rough diagram: Plane mirror------Object--...
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Studying curved mirrors. It's given that focal length equals half radius of curvature for concave spherical mirror, yet calculations show else

It is my first time studying reflection and the book states that for a concave spherical mirror, reflected rays parallel to the principal axis, $R$, pass through the focal point and the distance of ...
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Mathematical definition and notation of Fermat's Principle for least time

I was going through geometrical optics as it's a part of my undergrad course ,and I found about the Fermat's principle. The principle was understood but the mathematical equation given for it was not ...
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Deriving the thin lens formula from the lens maker formula

I've been studying refraction recently, and I faced some doubts regarding the thin lens approximation. The thin lens formula is given as : $$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$$ However, I also know ...
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Why angle of refraction parallel to base of triangle in triangular prism? [duplicate]

My textbook says that: At minimum deviation of a triangular prism, the refracted ray is parallel to the base of the triangle But I feel like it's only possible if the triangle is isosceles or ...
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How can solve to calculate position of image for any random point and random paraxial rays?

I am a high school student and I have a confusion related to optics {image formation via spherical mirrors) in all my books they say to find location of image its convenient to use the following rays&...
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How does one derive Fermat's principle of Least Time? [duplicate]

Fermat's principle states that the path taken by a ray between two given points is the path that can be traveled in the least time. I understand that Fermat's principle of Least time is crucial in ...
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What is optical path length? Does it make sense that the optical path length is variable or zero?

I've encountered an exercise where L(A,B) = sum of other OPLs that are parts of itself, and at the end we got that L(A,B) = 0?! But the definition is that L(A,B) = OPL = sum(...) = n×AB, so that means ...
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Is it possible to find the magnification of multiple lenses if the object is at infinity?

I understand the ray diagram of three lenses (converging, diverging, converging not stuck together) with an object at infinity, but is it possible to calculate the magnification of the entire system? ...
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Angle of Prism?

The definition of angle of prism is, "The angle formed due to two lateral faces of the prism is known as the angle of prism". My question is if there is an isosceles prism then which angle ...
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Reverse Vector Snell's Problem

Is there a simple way to reverse the Snell's-Equation-in-Vector-Form problem? I.e., given the incident and transmitted vectors $\,\mathbf{i}\,$ and $\,\mathbf{t}\,$ (both with norm = 1), find the ...
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Spherical mirrors or parabolic mirrors?

I am a high school student and have learnt about how curved surfaces reflect and refract (in "ray optics"). We were always told that these surfaces were spherical in shape, meaning they were ...
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Derivation in ray optics

How to derive the formula for magnification in spherical mirrors and thin spherical lenses? I already know the relationship between image distance (v), object distance (u) and focal length (f), in ...
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How to measure a 90 degree angle in a tilted image?

I look at an object through a microscope, which is not perfectly laying on the ground. I take a picture of it and try to measure if the object geometry has exactly 90 degrees at one of its edges. But ...

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