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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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Can light possibly bend to the other direction of the normal?

When light goes from a more dense medium to a less dense medium, it bends away from the normal, as in the image When light goes from a less dense medium to a more dense medium it bends towards the ...
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Lens simulator with geometrical optics [duplicate]

I'm looking for a lens simulator to see rays from geometrical optics, possibly easy to use. For now I'm playing with OpticalRayTracer that works perfectly for a preliminary simulation. I would like a ...
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2answers
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Double-slit diffraction: is $x$ measured from the centre to the fringe, or between the fringes on either side?

In using the formula $\lambda = \frac{ax}{D}$, is $x$ (the fringe separation) measured from the centre to the fringe, or between the fringes on either side of the centre? In other words, in the ...
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1answer
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Why is it necessary for all the light rays to reach the focus of a spherical mirror at the same time?

I've heard people say this stems out of fermat's principle of least time, if so, how? Note:I don't have great knowledge of ray optics, please explain as you would to a person just been introduced to ...
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Shadow of object placed Underwater [closed]

Suppose there is a cubical block placed inside a centre of the beaker which is filled with water to it's top.We place the beaker on a table and obtain it's Shadow on the ceiling.Will the shadow be ...
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Image of an Isosceles triangle kept on the focus of a u concave mirror

Consider the question and the diagram in the following link. Question What will be it's image? I got it for 2 points on the horizontal line, one will be at infinity. For the slant line, do we ...
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2answers
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Which side is convex in my plano convex lens?

So, I am building an optical system and have got a Thorlabs plano-convex lens (part # LA1172-C) with a 400mm focal length. This makes the convex side of the lens so flat that it is difficult for me to ...
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1answer
43 views

Lens design with few constraints

I'm not an expert in lens design. I need to build a lens having fixed the focal point $f$, the lens diameter $D$, the maximum thickness $d$, the refractive index $n$ and the half-angle $\theta$ ...
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Shadow of Partially immersed pole

I read that shadow is formed at opposite end if the sun rays are coming at an angle towards us Something like the above picture.But now while I'm studying geometric optics in a question where i need ...
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Why the first ring's radius appears to be too little in newton's ring experiment?

In newton's ring experiment we should be going to see a large number of rings with their converging radius. But the ring right next to dark fringe is way nearer than 2nd or 3rd which appears to be an ...
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1answer
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Why should refractive index of core be higher than that of cladding in TIR?

To confine the optical signal in the core, the refractive index of the core must be higher than that of the cladding. I failed to understand how and why does cladding refractive index matter since ...
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1answer
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Telecentric lens system with gaussian optics

I often use bi-telecentric lenses at work, which means both object-side and image-side chief rays are parallel. However, as I don't really have an optics background, I'm a bit baffled at how this ...
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1answer
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“Partial” Total Internal Reflection

Can partial TIR happen? Consider the image present in this link Here, at point D, TIR happens, but also there is transmission. Is "total" internal reflection a misnomer?
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How to find the radius of curvature of plano convex lens? [closed]

The information available about the lens are Refractive index n Aperture diameter d Maximum thickness of the lens t Is it possible to calculate the radius of curvature of the lens using the above ...
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1answer
29 views

Confusion regarding path difference by glass lab in YDSE

If in a YDSE experiment the setup is immersed in a medium $n_{med}$, and a glass slab of thickness t of another medium $n_{glass}$ is introduced in front of one slit, then is the path difference due ...
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1answer
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Validity of ray optics

Why don't we consider 3d objects or even 3d refracting surfaces(2d glass slab) in geometric optics .Why many phenomena is only valid for point size objects (such as refracting from curved surface)?
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Air wedge interferometer (Fringe separation)

From Hecht optics, From the setup, $ \alpha = \frac {d}{x}$ $--> d = x \alpha$ $d$ is the varying thickness of the air wedge The condition for constructive interference, $ ( m + \frac {1}{2} ) \...
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1answer
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Real and Apparent Depth

Why can't human eyes see bent light rays ? In real/apparent depth why do we think light is coming straight?
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Fringes of equal inclination (Haidinger fringes) Why is the interference pattern circular?

From Hecht optics 5th edition: It says 'With an extended source, the symmetry of the setup requires that the interference pattern consists of a series of concentric circular bands centered on the ...
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2answers
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Refraction of light from going to one medium to another

On the basis of ray theory can somebody please explain my why does light bend from going to one medium to another.Why can't it move in a straight line but with different speed ?
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Image Formation in plane mirror

I just read that in image formation by plane mirror the rays can't go above the height of the object and below principal? Whereas in concave/convex mirror the light ray can go above/below . Why is it ...
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1answer
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Simulating the physics of an imperfect eye

I am working on a project where the purpose is to show the most common ocular ametropia (myopia, astigmatism and farsightedness) to lay people. One of the demonstrations I would like to do is: the ...
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2answers
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Variable refractive index question [closed]

A ray of light travelling in air is incident at grazing incidence on a slab with variable refractive index, $n (y) = [k y^{3/2}+ 1]^{1/2}$ where $k = 1 m^{-3/2}$ and follows path as shown in the ...
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1answer
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Variation of Refractive index

We know that refractive index, for any medium, $$n=1/\sqrt{\epsilon\mu}.$$ Also, according to Cauchy's relation $$n=A+B/\lambda^2,$$ where $A$ and $B$ are constants related to the medium. ...
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6answers
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Can an electromagnetic wave travel less than the speed of light and yet perceived by the eye as a light?

When an electromagnetic field passes through different mediums, it is known that it will refract. And during refraction - since its frequency is kept constant - the only parameter that changes is its ...
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0answers
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Do virtual images exist in the real world? [duplicate]

I have been reading an article here in physics stack exchange that talks about if it is possible to see virtual images, and i read an answer saying it is actually your brain that understands the ...
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1answer
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Calculating maximum allowable velocity of an object during holography

I am working through some questions in preparation for an upcoming exam and the following has me doubting myself: An experiment takes $x$ seconds to create a hologram of an object using $\lambda$ nm ...
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3answers
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When does the retina fail to recognize images of two closely separated points as distinct?

Our eye is a lens and lenses have a resolving power. The resolving power of a lens, physically speaking, is related to how good two closely separated points A and B can be distinguished as separate. ...
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1answer
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Calculating refraction between numerous media

Last year, our teacher made us an exam to check our knowledge in light reflection and refraction. I don't perfectly remember it, but I know that one of the exercises included a ray with its angle of ...
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0answers
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Zebra and Donkey Watching [closed]

Suppose I have a white donkey in front of me. Say i paint black stripes on the objective of my camera lens and click a photo of it. The context of this question is that when we cover a lens ...
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2answers
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Where does dispersion actually take place?

Out of 1 & 2, which is most accurate? And, out of 3 & 4, which is most accurate? Do they both agree with each other? Please explain?
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Radius of wavelet using Huygen's principle

I was trying problem 1.6 and couldn't solve it. Any help is appreciated. My effort : I considered a point $P_1$ at distance y from the x-axis and another point $P_2$at a distance $y-\delta y$ from ...
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Radius of curvature of a spherical mirror using only magnification?

Given that an object of heigh 1cm is placed in front of a spherical mirror and produces an upright image of height 0.2cm, find the radius of curvature of the mirror. I know that $ M = \frac{h_i}{h_o}...
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1answer
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Image formation in Ray Optics

Can a refracted ray and a reflected ray form an image( different incident rays coming from the same object, one sufferning reflection and other refraction)? What is the criteria for forming an "image"...
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1answer
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Finding intensity of laser after round trip in cavity with single mirror [closed]

I came across a question in a text book today, and was wondering if someone could maybe check to see if my physics and workings are correct, as I am getting a intensity value greater the what going ...
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1answer
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What is a 3rd-order Fresnel lens?

The NPR News article and podcast Job Opening: Seeking Historian With Tolerance For Harsh Weather, The Occasional Bear talks about the Split Rock Lighthouse. That Wikipedia article links to the image ...
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1answer
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Transfer matrix

Let's suppose I have a transmission curve, $T$. How could I calculate the resulting transmission $T_\text{final}$ if the light propagated trough a much longer distance in the same media and eventually ...
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1answer
23 views

Virtual and Real Images

I am well thorough with the concept of virtual and real images for a single lens/mirror. However I don’t understand how it exactly works for complex system of lens .eg-two or three lens with a ...
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0answers
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Why is the luminous flux in a closed sphere equal when the light bulbs are the same Watt regardless of the radius?

Why is the luminous flux in a closed sphere equal when the light bulbs are the same Watt regardless of the radius ?
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1answer
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Why is luminous intensity dependent on the incident angle?

Why is luminous intensity dependent on the incident angle which hits a surface of a specific area?
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1answer
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Feynman Lectures Vol. 1: error in the formula for resolving power?

In chapter 27 of Feynman Lectures on Physics Vol. 1, section 7 on resolving power, Feynman states the rule for optical resolution: two different point sources can be resolved only if one source is ...
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Confusion in sign convention of magnification?

A concave mirror forms a real image three times larger than the object on a screen. Object and screen are moved until the image becomes twice the size of object. If the shift of object is 6 cm. Find ...
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3answers
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Geometrical Optics: Infinite Rays

Normally in ray optics, we draw a parallel line from the top of the image to the lens and stop when this line intersects an angled line (drawn from the height of the real object) and intersects. ...
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1answer
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Proof of interference fringes take the same shape as the shape of the film? [closed]

(First of all I should mention time talking about interference between two reflecting rays thinking e.g. Newton's rings.) Studying wave optics I have found that at the fringes take the same shape as ...
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Predictions followed from Fermat's Principle, according to Feynman

In his book Lectures on Physics, Feynman mentions two predictions followed from Fermat's Principle (chapter 26-4). 1) Given three media air (1), water (2) and glass (3) with indices measured against ...
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1answer
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Comparing a wave's wavelength and the dimension of a medium in which the wave travels

Is making a comparison in between a wave's wavelength in a medium, and the medium's own lengthscale only useful when one needs to check whether the laws of geometrical optics are applicable? In other ...
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1answer
27 views

Longitudinal magnification

I want to prove that if an object is small in length and lying along the principal axis then $M = -\frac{dv}{du} = -\left(\frac{v}{u}\right)^2$ where $M$ is the longitudinal magnification
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2answers
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How is depth perception linked with the separation between our eyes? [duplicate]

I came across a comment online which mentioned that one of the main benefits of having 2 eyes is that we can perceive depth. I tried closing one eye and seeing for myself if somehow everything would ...
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0answers
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Why does sunlight on these windows form caustics with a seemingly hyperbolic pattern?

I noticed these caustics outside my office about a month ago and took pictures: one facing towards the sun and one facing towards the reflective surface (a set of double-paned windows). The seemingly-...
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0answers
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Interference using composite lens

I encountered a question while attempting an exam. I cannot really understand how to go about it. It is clear that the concave part forms the image at a distance $3 \lambda /2$ behind the lens, and ...