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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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18 views

Why do all rays of light parallel to principal axis of a spherical mirror meet at focus?

The reflected rays of light are not parallel or coinciding to each other, so they will have a unique solution(point of intersection) but why is that point of intersection half of centre of curvature ...
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31 views

What does it mean that image if formed in front of mirror

Today my teacher told me about plain mirror that distance of image formed(inside mirror) is same as distance of object. And clearly I can understand like the frame of mirror shown here is a door and ...
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Question about adjusting focus on augmented reality

I am working on a project and I am trying to build augmented reality glasses. I have a question about focusing the projection from screen and the real object on the far distance at the same time. How ...
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Difference between phase variation and phase deviation

I was wondering whether there are differences between the terms phase variation and phase deviation of a wave. If we have an equation of a wave which is incident on a plane given as : E(x,t) =Eo $\...
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Sign convention for spherical mirrors

What is the sign convention for this formulation of the spherical mirror equation? $$1/i + 1/o = 1/f$$ f is negative for convex mirrors. i is image distance. o is object distance. (How can the ...
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Formulas with complete sign conventions for spherical mirrors and thin lenses

I'm looking for two things: Something like the third equation in the chosen answer in the link, but for spherical mirrors, and Something that covers conventions for the radii of curvature and focal ...
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1answer
33 views

Vision bluriness

I don’t know much about vision so I hope one of you guys could clarify me… When people who have vision problems look at an object without their glasses, they’ll see this object with a certain level ...
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1answer
40 views

What is the physics behind Samsung Galaxy Axx-series “3D Glasstic”?

How does back cover of Samsung Galaxy A30 transform light into those wavy white lines? I hope you could draw a schema of incident and reflected light with the answers.
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Newton's explanation for interference [duplicate]

If Isaac Newton believed that light is a particle, then how did he explain the interference phenomena?
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How to simulate an inverse square law dependence of radiant flux from sampled rays?

I am trying to simulate (MonteCarlo integrate) the following scenario, see sketch below (as prequel of a somewhat bigger simulation). Assume a small (point) L'Ambertian emitter, i.e. the radiant ...
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64 views

Fermat's Principle of Least Time

I was going through the Feynman Lectures on optics when I came across an explanation for Fermat's Principle. I did not fully understand the explanation- can someone please break it down in a simpler ...
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2answers
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Sunrays through clouds paradox [duplicate]

So I have a layman question. If we look at the angle of the sun rays, doesn't sun seem much closer than it is [150 million kilometers] cant we take those angles that the sun makes with the earth, ...
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Fermat's Principle: no first-order change in time?

I was reading the chapter on Fermat's principle in the Feynman lecture series. The principle is stated along these lines: "The correct statement is the following: a ray going in a certain ...
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Satellite image anomaly

This is a satellite image of somewhere in West Texas: See the localized Red-Green-Blue feature on the road? What could have caused this?
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How do sharp objects deflect radio waves?

This technology is used in stealth aircraft.The pointed nose of aircraft deflect those incident waves but not reflect back.Also speculate in case of rounded object with those waves.
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Focal plane of ideal thin lenses and spherical mirrors

Recently I was studying about optical instruments and in my book I came across a point which stated that When non axial parallel rays are incident on an ideal spherical mirror at a small angle or a ...
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1answer
22 views

Calculation of emergent angle of prism

Is there a way to calculate emergent angle of an equilateral prism (non-experimentally) ? I know that one equation that might be helpful is $$\angle D + \angle A = \angle i + \angle e$$ But a single ...
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1answer
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The change of focal distance as a result of adding a substance

I have a given focal distance between lens and an image sensor (in air). Now I add a protective glass with a known refractive index and width between the lens and the sensor. How can I calculate the ...
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Question about zooming out with optical lens

I need some help. I am working on a project and I am wondering if it is possible to make an object to look 100 times far away than it is actually using lens (or more than one lens). The lens (or ...
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Littrow Configuration Spectrometer

I have been studying the design of a spectrometer using a transmission diffraction grating. I stumbled upon this link, https://ibsen.com/technology/spectrometer-design-guide/. It explains a ...
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2answers
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If a point forms a point image in curved mirror then how do images of objects in curved mirror get magnified?

If we assume a object lying between the pole and focus of a concave mirror , then a virtual,enlarged and erect image is formed. Now by ray diagram the top of the object form a virtual point and so ...
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Scattering of light rays off a corrugated surface

I am currently facing the following problem: Suppose I describe the shape of a corrugated surface with a certain function: \begin{equation} y_\mathrm{surf}=A\sin(kx); \qquad x\in(-\infty,\infty) \...
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Fermat's principle of least time for reflection and refraction [duplicate]

In discussing geometrical optics, Fermat's principle of least time is often used to solve problems and is generally used as a replacement of laws of reflection and refraction. Fermat's principle is ...
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1answer
58 views

Why do the rail tracks seem to converge and vanish? [duplicate]

Why do railway tracks seem to converge at a far away point? Can this phenomenon occur with a very far away tall wall (considering I stand on a flat plane, not the curved surface of earth). Isn't ...
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How are thin film interference patterns observed?

I am having a hard time studying optics. My main difficulty is how images are formed. In Pedrotti's Introduction to Optics, he shows a diagram of this experiment: According to the diagram, all light ...
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1answer
39 views

Image formation of object on itself by a system of a lens and a mirror

Suppose there is a lens and a mirror. An object is placed in front of this system (nearer to the lens). If the final image of object (refraction, reflection and again refraction) is formed on the ...
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Parallel rays hitting a parabolic mirror at an angle [closed]

I was thinking about parallel rays hitting a mirror that has a parabolic horisontal cross-section and a linear (straight) vertical cross-section. I can't understand what would happen if the rays came ...
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Rainbow angle wider than 90 degrees?

A rainbow is formed at the boundary between two materials that bend light differently, such as water and air. Using the laws of optics, you can find a formula for the angular size of a rainbow in ...
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142 views

Ray Tracing and Rotations

I would like to be able to write the matrix operations to be able to define the first arm of the picture below. How can I do that? I have learned beam physics, have read Siegman's Lasers, if that ...
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1answer
52 views

Focusing a Gaussian beam into a nonlinear crystal

Boyd analyzes in his book (Boyd's book), section 2.10.3, the case of harmonic generation using a focused Gaussian beam and he mentions that an analytic solution can be evaluated for certain special ...
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Problem related to combination of lens & equivalent focal length and lens maker's formula [closed]

in between two equiconvex lens( made of glass) of focal length of 20cm there is a layer of water which also acts as a convex lens.The whole figure is surrounded by air. Find out it's equivalent focal ...
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Gaussian Beam propogation in a fiber

If we suppose that a Gaussian beam traveles in the fiber with diagonal end as it shown in the image, so I have several questions: 1- Do we get in the end of the fiber Evanescent field (Total ...
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2answers
125 views

Snell's law and Fermat's principle

I have read this sentence on a book about the Snell's law of refraction, referring on a ray that passes from air ($n_1=1$) to glass ($n_2=1.55$): "Snell's equation can be derived from Fermat's ...
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Thin Lens Approximation [duplicate]

Why is ray travelling through pole passes undeviated?( not changing any direction) ( this was asked in kvpy interview)
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1answer
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If final image of object is forming at viewer's eye, where will viewer see that object?

If an object is kept at centre of curvature of convex lens and a viewer is present at centre of curvature of other side then where will he see that object? I think he will see the object at it's ...
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DUAL IR BEAM DETECTORS and SUNLIGHT INTERFERENCE

I have a dual beam IR detector with the receiver well protected from direct sunlight and still get false triggering. (This is outdoor equipment) I have tried single beam sets outdoors in the past ...
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Why do parallel light beams converge at the focal point of a curved mirror?

Can someone prove that all parallel lights beams reflect back and meet at point the point $F$? Any help would be appreciated.
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Can a LGL (Lens-Grating-Lens) spectrometer have a non-zero geometry?

I am designing a transmission grating based spectrometer. Can the angle of incidence on the grating (alpha) be unequal to the diffraction angle (beta)? I didn't think that they could be varied as i ...
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Relation between distance, sizes and angular diameter?

If we pick up a ruler and look at it and at the sky at the same time we can have the moon be completely inside the ruler or if we add distance between the ruler and us the moon will become apparently ...
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Poynting vector flux in a tube (geometrical optics)

Let's consider the following tube (defined as the solid described by two arbitrary surfaces dA1 and dA2, and by all the rays which connect their boundaries): I read in a textbook that, because of ...
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27 views

How Gaussain beam exaclty be after diffraction between two mediums?

How it will be the refraction of the Gaussian beam, does one of its sides will go in distortion, and which equations can predict this distortion? Sure I have to use Snell's law to know the angle but ...
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1answer
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Reflected plane wave intensity air/water?

Good morning. I am evaluating this situation. A plane wave at $f=60$ MHz coming from the air affects the sea with an angle $\theta_1=80°$. I know $n_{air}=1$ and $n_{water}=1,33$. I've applied the ...
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46 views

If white light travels from glass to vacuum will there be dispersion?

Will light disperse on traveling from glass to vacuum considering incident angle that is less than the critical angle (i.e. no total internal reflection)?
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1answer
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What is the difference between longitudinal chromatic aberration and spherochromatism?

In lens design textbooks, a distinction is often made between longitudinal chromatic aberration and spherochromatism. (See for instance Kingslake's lens design book.) What is simple way to understand ...
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Gravitational lensing in the form of optical equation $\frac{1}{p} + \frac{1}{q} = \frac{1}{f}$? [duplicate]

Gravitational lensing and light deviation is a well known subject in General Relativity. I'm wondering if the null geodesics equation could be recast into the classical lenses equation: \begin{...
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3answers
104 views

Lens with focal length 0

I have been wondering about a limiting case of the focal length. Specifically, a lens with a focal length of $0$. Could that exist in real life, and what would be its meaning? Also, what does it mean ...
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Light ray through glass tube

Is there a way possible that light ray goes from glass tube to air undeviated in a straight line? I made few ray diagram but could not find a possible way
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28 views

Final Image Position with Multiple Lenses

I am confused on how to calculate the final image position after the two lenses. I understand that the image position of the first lens can be treated as the object position of the second lens, but in ...
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1answer
163 views

How to determine the focal length of a combination of two convex lenses separated by a distance $d$ experimentally without formula?

I have done this experiment to find out the equivalent focal length of a combination of 2 convex lenses of slightly different focal length and have applied the formula for the equivalent focal length ...
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Why does the images of slit slip down in bottom as we move the lens?

Why does the images of slit slip down in bottom as we move the convex lens in the experiment of "determination of wavelength of sodium light by fresnel biprism experiment". We made the system coaxial ...