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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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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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41 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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What will be the refractive index for a symmetric bi-convex lens where focal length is equal to radius of curvature? [on hold]

This question was asked in one of my high school quizzes, and it is most likely wrong, which is why I am trying to clarify. I had used the lens maker's formula as... $$\frac{1}{R}=(\mu - 1) \frac 2R \...
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Glass plate in aquarium tank's apparent thickness? [closed]

A glass plate (n=1.66) rests on the bottom of an aquarium tank 12cm deep. The plate is 8cm thick, and is covered with a layer of water (n=1.33). Calculate the apparent thickness of the plate. My ...
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70 views

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
25 views

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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43 views

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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Geometric phase of an optical fiber or the space curve

Hi everyone I am trying to understand the geometric phase along an optical optical fiber. I am a geometer and I am almost ok with the geometric part but I have some diffuculties to extract physical ...
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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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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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52 views

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 ...
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working to understand virtual images

I'm starting to understand how to use lenses a bit more, but I'm still pretty lost. I'm building a project that's extremely similar to this one with the implementation. I think my biggest challenge ...
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How to check whether the telescope is properly collimated?

I have made a refractive type telescope. I have roughly checked that whether it is properly collimated, which is nothing but the conventional method. I looked through the telescope at a distant object ...
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Optics of an all-sky camera

I'm curious about the optics of an all sky camera like this one or this one. My suspicion is that the sensor has an inherently wide field of view - the former has a lens that's 1.55, which doesn't ...
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How do we distinguish virtual images?

I understand that virtual images are named because the rays that result from the reflected image "appear" to be emanating from an object (or resulting virtual image) behind a flat or convex mirror. ...
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Value of complex angle in Snell's law

According to Snell's law: $$\sin \theta_t = \displaystyle \frac{n_1}{n_2} \sin \theta_i$$ where $\theta_i$ is the incidence angle in medium 1 and (after the ray crossed the interface between medium ...
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2answers
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image formation by lenses

Why is the image formed by an object as described in the picture can be derived only from these three ray of lights?Every point on the object has multiple ray of lights going in every direction, how ...
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Is the focal length of a lens for light in one direction necessarily the same as for light in the opposite direction?

Suppose there is air at one side of a lens, and water at the other, such as in the human eye. Is the focal length for light in the direction from air to water then different from that for light in the ...
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What will happen to an image of an object if we neglect paraxial approximation

Suppose there is a swimming pool filled with water to the brim . We try to observe a small insect at the bottom pool with our eyes. Now generally if we view for small angles of incidence or under ...
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1answer
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Ray transfer matrix for non small angle

As I could understand, we can trace rays through optical elements using the ray transfer matrices . However, the references I could find online seems like it considers the angles to be small (Sin(t) = ...
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1answer
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Acquire gradient data of a surface from deflection measurement

. In the figure above, a laser beam with source at point $I$ falls on a surface (DUT) at point $P$ and gets reflected. The reflected ray falls on the center of camera at point $R$. From the figure it ...
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4answers
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Doubt about ray diagrams

In a ray diagram, 2 rays are considered enough to locate the image of a point on a given object. But how can we say that the rays other than the one we drew will meet at that same point? I guess ...
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How does the reflection coefficient change with scattering and absorption?

My professor of Biomedical Optics course asked us to think upon the evolution of the reflection coefficient with the absorption coefficient $\mu_a$, the reduced scattering coefficient $\mu_s'$ and the ...
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How does apparent depth depend on viewing angle?

In derivations of apparent depth and articles on refraction the approximation that the viewing angle is small is made in order to derive that $$D_a = \frac{n_v}{n_o} D_o,$$ where $D_a$ is the ...
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Bragg diffraction form an “inclined” crystal plane: which angle to consider?

Consider Bragg diffraction form an "inclined" crystal plane (i.e. not perpendicular to the normal of the crystal). I was sure that the angle of diffraction $\theta$ in bragg's law must always be ...
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61 views

Huygens' principle

How do we know that the angle ADC is right angle here?
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Why do my glasses make the ground look tilted?

I just started wearing glasses to correct my myopia today. I have -0.25 spherical and cylindrical power in my right eye and -0.5 spherical and -0.25 cylindrical in the left eye. Everytime I look at ...
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If the Sun moves across the ground at 0.25 nautical miles per second, why do shadows move very much slower? [closed]

This title has been discussed previously on this site here. Question: Shadows from the sun moves fairly slow across the ground. Maybe a centimeter per sec. however, I calculated that the sun is ...
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1answer
74 views

Huygen's Principle, Snell's law and velocity of light

Can you deduce Snell's law from Huygen's Principle without knowing in which medium the velocity is going to less? Of all the derivations I have seen of Snell's law using Huygen's Principle (light ...
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2answers
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Example in which light takes the path of maximum optical length [duplicate]

According to the modern version of Fermat's principle,"A light ray in going from point A to point B must traverse an optical path length that is stationary with respect to variations of that path.".Is ...
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1answer
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Can Fresnel zone plates be used as collimators

I quite often use the principle in physics that (outside of thermodynamics), all laws of physics are time-reversible. And so, when looking at collimating microwave light, I though that it might be ...
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How is the component of a wave vector parallel to an interface made to always be real?

This question stems from what I've seen as the definition of a wave vector and from not being able to reconcile how, when the incident medium is lossy, the parallel component can always be real. Let's ...
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1answer
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The focal length of spherical mirrors

How are the focal length, the object distance and the image distance related?
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2answers
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Formation of Image by Mirrors

We know that,Concave mirror reflects the light rays and the image is formed in front of the mirror but we see the image in the mirror itself.So how it is possible and if i am wrong at somewhere then ...
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2answers
466 views

Snell's law in vector form

Snell's law of refraction at the interface between 2 isotropic media is given by the equation: \begin{equation} n_1 \,\text{sin} \,\theta_1 = n_2 \, \text{sin}\,\theta_2 \end{equation} where $\theta_1$...
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1answer
97 views

What is the difference between horizontally/vertically polarized light and s/p polarized light?

My doubt comes from a discussion we had in class about the Brewster angle, glare effect produced by the reflection of sunlight on water and polarizing sunglasses. So an unpolarized electromagnetic ...
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1answer
108 views

Spherical Refracting Surfaces

Why when given a question to find the image of a point object in a spherical refracting surface do you have to consider that there are two surfaces refracting the light? I assumed that one could ...
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How to make light beam to be super narrow?

I am doing a project to use a regular laser beam to be super narrow (25um diameter). I am thinking to use some lens setup to do that. Does any lens setup can make a 5mm diameter laser light source to ...
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Difficulty in understanding an optics question

So here's the question:- A thin film of transparent material of refractive index $1.52$ and thickness $0.42\ \rm \mu m$ forms a thin coating on glass of refractive index $1.60$. It is viewed by ...
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If the velocity of light is different in different medium is it wavelength changes or frequency changes?

We know that the velocity of light is equal to the product of it's wavelength and frequency. And when light goes from vacuum to any other medium it's velocity changes depending the mediums refractive ...