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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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Optics that translates object to image by a constant amount

For some application I was interested in an optics s.t. for any incoming ray the outcoming ray is parallel to the incoming ray and shifted by a distance $d$ (independent of the incoming ray) along the ...
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How to know if a thick lense system is divergent or convergent

I know that the sign of the effective focal lenght (f) of a lense will determine if a that lense is divergent(f<0) or convergent(f>0), but with a system made of a combination of thick lenses and ...
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The ideal shape of a plano-convex lens

What's the type of the ideal shape of a surface of a plano-convex lens to focus a parallel beam at the point? Considering the lens turned its flat side to a beam. Surely it must be aspheric: ...
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Huygens’s principle [closed]

On the application of Huygens’s principle with an incident wavefront on the mirror, we see that wavelets are emitted at each point as shown. My question is how can the direction of propagation of the ...
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How does a single photon behave propagating through glass?

Take a normal pane of window glass and a photon somewhere within the visible range. My limited understanding is that when light passes through glass one shouldn't think of little spheres travelling ...
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Question regarding reflection in a curved mirror

Given the mirror equation, it's stated that in order to contruct the image of an object we must launch a light beam parallel to $x$ axis and that it will reflect back at the focus of the circle. This ...
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Solving simple lens problem with matrix formalism [closed]

I tried to solve the following problem with the matrix formalism, but I keep getting the wrong answer. I have an object $A$ in some medium with index of refraction $n$, a distance $L$ away from some ...
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Why do prism split light at angle instead of curving it?

I assume that when light goes through matter, it doesnt really slow down, but the waveform is pushed back due to some resonance with the atoms. EDIT: Interference is probably a better word than ...
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Seeing virtual image in convex lens of object kept beyond focal point

Beyond the focal point, $f$, a convex lens only forms real image. However, I see an inverted virtual image of a distant object when looking at the lens from a distance. If the image of the distant ...
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Can Snell's law be said to fail in this condition?

I ran into a question in my textbook which asks me "when does Snell's law fail?". My first reaction was that it's a law, it can't fail but they gave the solution as the condition when light rays are ...
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Derivation of the relationship between snellen rows and diopters

Here's an incorrect derivation of the conversion from rows of a Snellen chart to diopters -- this derivation results in the correct sign but too small a value: Interpret ...
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Is it possible to make a source of light such that it only emits one ray of light?

I am just a high school student trying to self study, so please excuse me if you find the question silly. I don't really need to explain my question.I am just asking if we can make a source of light ...
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Which of these 2 methods for calculating the focal length of a concave mirror is more accurate?

I have done an experiment to measure $f$ the focal length of a concave mirror. I have a list of 8 values for $u$ the object distance and 8 values for $v$ the corresponding image distance. I ...
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Bending of light Ray in radially varying refractive index [duplicate]

If light passes near a massive object, the gravitational interaction causes a bending of the ray. This can be thought of as happening due to a change in the effective refrative index of the medium ...
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Need a sample of a Probability density function in Oblate Spheroidal Coordinates

I need to develop a probability density function in Oblate Spheroidal Coordinates. That is, the volume under a this function surface is equivalent to 1 . Any idea how to propose this ? In a two ...
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What does it physically mean for an object to be placed at infinity?

Hi Physics Stack Exchange Community. I am new to studying Optics. In my textbook there is constant mention of the images of objects placed at infinity for Concave, Convex Mirrors and Lenses. But it is ...
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Geometrical optics problem [closed]

I Just wanna know the general approach to these problems, Two plane mirrors of length L are separated by distance L and a man $M_2$​ is standing at distance L from the connecting line of mirrors as ...
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What is Snell's window?

How an underwater observer can see only a circular "window" and also can't see anything above the seperating surface ? Does the "window" depends on the depth ?
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Exercise in Loudon's Quantum Theory of Light

This is problem 3.3 in Loudon's Quantum Theory of Light. A prerequisite for this is problem 3.2. I will state both of them here. 3.2 : Consider the beam of light produced by excitation of two ...
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Explanation of problem 2074 in Lim-Yung-Kuo's Problems and solutions in Optics

A pinhole camera consists of a box in which an image is formed on the film plane which is a distance P from a pinhole of diameter d. The object is at a distance L from the pinhole, and light of ...
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Sign convention in combination of lenses

The problem statement: Two convex lenses, each of focal length 10cm, are placed at a separation of 15cm with their principal axes coinciding. Show that a light beam coming parallel to the principal ...
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Is focal length of Plano Concave lens $f=\cfrac{R}{\mu - 1}$ or $f=\cfrac{R}{1 - \mu}$

Let the radius of curvature of the concave part of the lens be R. Then when using the lens makers Equation, $$ \cfrac{1}{f} = \left(\cfrac{\mu_2}{\mu_1} - 1\right)\left(\cfrac{1}{R_1} - \cfrac{1}{...
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What is the optical Lagrange invariant of an afocal system?

I am solving an optics exercise that requires to design a Keplerian telescope with a given magnification M (negative), a certain object size L and the restriction of not having lenses faster than F/1 (...
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Fringe pattern in Michelson interferometer

It's given that CA - CB is d, the angle CAE is $\theta$. (E is not on the normal of mirror M1). I want to find the condition for maxima at E (as a function of $\theta$). I tried finding the path ...
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What should be the shape of an axisymmetric solar reflector that provides a uniform flux on the surface of a circular cylinder placed on its axis?

I was wondering about creating a solar concentrator with an antisymmetric concave shape that is able to focus the collected light onto a circular cylinder positioned on the concentrator axis. The ...
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Comprehensive Nature of Light: Transverse vs Longitudinal Waves and Ray Optics

----------I understand that we consider light as a transverse wave in the sense that light is composed of E&M fields oscillating perpendicular to each other and the direction of propagation. And I ...
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Refraction on the edge of mediums

Say I have this setup : Here a light ray (in red) is incident on the point A in such a way that it is collinear with AB, and the indices of refraction are as mentioned in the figure. So my question ...
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1answer
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Why do we neglect higher order terms in Cauchy's Equation?

Cauchy's Equation for finding the refractive index for a light of given wavelength is: $$n(\lambda)=A+\dfrac{B}{\lambda^2}+\dfrac{C}{\lambda^4}.....$$ This formula however is simplified to $n(\...
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1answer
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What aberration causes the common “cross pattern” in astronomy images? [duplicate]

I am trying to understand the origin of the plus/cross-sign aberrations commonly seen for point sources in astronomical images, even ones created with professional-grade, high-quality optics. The one ...
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1answer
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How do these toroidal reflectors form an image in two dimensions?

A torus has a major and minor radius, which means a symmetric section of one will have different focal lengths in its focal plane, or astigmatism. If it's from the "outside" of the torus (where you'd ...
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Ray-tracing on a thick lens [closed]

I'm having some troubles drawing down the main rays on a thick lens. In particular I don't understand if the parrallel ray which comes from the right will start to divert intercepting the MP1 or the ...
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1answer
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If you have 2 lenses, is it better to place the stronger lens first or the other way around?

I need to focus a laser at a certain distance. But everytime I perform the experiment, the distance between the laser and the surface will be slightly different. Therefore I will fix the lens with the ...
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If we shoot to photons to a surface, in which conditions we can differentiate the points where the photons collided with the surface?

Now, I heard this example from one of my professor 4 years ago when I first entered university, and at that I had some objections (and I still do), because, I think, if we flick our wrist fast enough, ...
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Identifying real and virtual images (convex lens experiment)

I m really confused between virtual and real images. While doing a convex lens experiment using optical bench (I have attached an image), when I look through the lens I see an inverted image. As this ...
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1answer
48 views

What is prime focus of a telescope

Telescope here refers to a system of two convex lenses. In one of the problems I wanted to solve, it is given that "a Barlow lens of focal length $f_{b}$ is placed at a distance $D < f_{b}$, from ...
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Back Focal Plane After A Convergent Lens

Acutually this is related to computer simulation, especially MATLAB. I am very confused, assume a plane wave passes through a convengent lens, where the propagation direction is parallel to paraxial ...
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Reflection Vector (Ray Tracing)

Snell's law of refraction at the interface between 2 isotropic media is given by the equation: \begin{align} \tag{1} n_1 \,\text{sin} \,\theta_1 = n_2 \, \text{sin}\,\theta_2 \end{align} $\qquad$ ...
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number of photons per area: after reflection != twice the distance

Say we have a light source emitting $N$ photons per unit area. In the first case, the photons are reflected at a distance $r$ from the source and measured again at the source. Divergence caused the ...
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How does the diaphragm in a camera work?

I think I am quite good at math and understand basic geometry, but I have problems understanding the function of a diaphragm in cameras. Let's say a camera is in a specific state. It captures the ...
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2answers
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Significance of image position

Consider the case of image formation in the convex lens when the object is placed between f and 2f its image will be formed beyond 2f on the other side. And the image position is said to be the point ...
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1answer
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How does Fermat's principle of least time come from this statement? [duplicate]

In Wikipedia Fermat's Principle is stated as: A ray of light prefers the path such that there are other paths, arbitrarily nearby on either side, along which the ray would take almost exactly the ...
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Where is the point of Incidence?

As you may know that critical angle is the angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally ...
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2answers
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The Plane Made Up by the Surface Normal of the Boundary and the Propagation Direction of the EM Radiation

My textbook says the following: Reflected light consists of two contributions: the first is light that is polarised parallel ($R \pi$) and the second is light that is polarised perpendicular ($R \...
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Seeing image in plane mirror

I recently came across this problem in which we are asked to tell if an eye (of negligible aperture) will be able to see the image of a point object in plane mirror. [Also the question (because of pt ...
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The diffraction angle of toroidal grating

I have a 300 g/mm toroidal grating (r=100 mm, R=920 mm, h=19 nm, c/d=0.51). I want to know the diffraction angle of 800 nm and 80 nm light when the AOE (angle of incidence) of them is 85 degrees, i.e. ...
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2answers
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Light hitting a GRIN (Gradient-index) lens at the optical angle

In the image below, rays of light are hitting the GRIN (Gradient-index) lens at the optical angle and then converge towards the optical axis. Why do they do this? The refractive index is only a ...
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Why does light go in the path where time is minimum and not maximum?

On deriving Snell's Law from Fermat's Principle there is a part where $\frac{ds}{dt}=0$ where $s$ is the distance gone by light. But the principle states that light takes the path where it takes ...
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Relation Between Speed of Light & Reflected Angle (Fizeau–Foucault)

I have a bachelor's in physics & its recently struck me that I do not understand, semantically, what phenomenon allows us to measure the speed of light through air in a small room with a laser and ...
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Magnifying power of a microscope for a farsighted person

I was doing some problems on optical instruments and in one of the questions it was asked that if a simple microscope(magnifying glass) has a magnifying power 5X for a normal relaxed eye.. what will ...
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Derivation of the index of refraction of glass as a function of rotation angle and number of fringe transitions

Recently, I've looked at how the index of refraction of a piece of glass can be related to the angle of rotation from normal incidence and the associated number of fringe transitions through a ...