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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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: (I apologize for the bad quality of ...
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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 [on hold]

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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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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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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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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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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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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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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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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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
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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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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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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 ...
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Focal length of A concave Mirror

What will happen to the focal length of concave mirror if it's inner side (reflecting side) is filled with a liquid of refractive $u$ up to a height $h$? Also, in a lens mirror combination (which are ...
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Lens Formula for thick lens

My textbook states that for thin lens formula of lens is i.e $\frac{1}{v}$ - $ \frac{1}{u}$= $ \frac{1}{f}$ and for thick lens $ \frac{1}{v-t}$ $ -\frac{1}{u+t}$ $= \frac{1}{f}$ While the ...
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Why do P-waves cross each other for small angles?

The following is an image produced by ObsPy of P-waves entering the earth just below the surface at small angles depicting the problem: I wish to understand why the P-wave rays cross each other at ...
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Why doesn’t a normal window produce an apparent rainbow?

When light refracts in a prism it creates a rainbow. My question is, why don’t all windows or transparent objects create this dispersion, i.e. why is the refractive index dependent on frequency in a ...
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How does looking glass work?

There's this really cool optical device That let's you view true volumetric 3D on a screen made of thick glass: More details and pictures for Looking Glass could someone explain how this device ...
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Polishing Spherical Refracting surface vs Lens

My text book states that When we polish a spherical refracting surface (sphere) it doesn't behave as spherical surface and mirror .It still behaves as spherical surface. The polished side is just ...
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Why does a prism refract light into a rainbow? [duplicate]

Why does a prism refract light such that the different frequencies of light “spread out”? The same goes for rainbows, why do the raindrops “spread out” the different frequencies of light?
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Image formation and focus

It is known that an image is in focus (and it results sharp and clear) only at the focus, in which all rays intersect themselves. Why do we see sharp images only at the point in which the rays emitted ...
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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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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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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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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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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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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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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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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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“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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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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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} ) \...