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 to find the principal axis of the pieces of lens after billetsplit cutting?

I was reading about lens from a book . There I couldn't make about the principal axis for billetsplit cutting of lens . As it can be seen from the above image that two lines L1 and L2 are drawn and ...
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Why do we have to include sign while calculating image position due to refraction by a lens? [closed]

When we calculate image position due to reflection by a curved mirror or due to refraction by a lens, we have to include the sign of the object's position. However, while deriving the equations that ...
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Abrupt change in refractive index

I have seen in some antenna courses that an interface between two dielectrics with an abrupt change of permittivity is usually described as an equivalent perfect magnetic conductor, though which no ...
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Pointing a laser to a mirror on the moon in spite of refraction by earth's atmosphere

I was reading that the Apollo missions left a laser reflector (Mirror) on the moon for scientific use. Having read some of the controversy here and elsewhere about lasers being affected by refraction ...
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Limits of zooming in (for camera/telescope)

What limits the ability of a camera/telescope to zoom in on distant objects? The question is twofold: What zoom really is? Firstly, I would like to gain clear understanding of what we mean by zoom ...
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Circular inversion and spherical mirrors

The object distance ($u$), image distance ($v$) and the focal length of a spherical mirror ($f$) are related by the well-known formula (using the appropriate sign convention): $$ \frac{1}{u} + \frac{...
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Number of images formed when two mirrors are placed at an angle

The formula for calculating the number of images formed when two mirrors are placed at an angle $\alpha$ is $360/\alpha$. My question is how many images will be formed when it is a fraction? My ...
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How does focal length affect magnification?

My answer would be the longer the focal length, higher the magnification will be, resulting in a larger image. But in a ray diagram, how does it look? I am searching for a comparison of ray diagram ...
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Finding the Focal Length of a Thick, Plano-Convex Lens

The lens maker's formula takes into account the thickness of a lens. However, if one surface is planar, its focal length should be infinite. But that means that with the below formula, the thickness ...
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Inconsistency in ray diagram

This example purports to show reflection of light rays from a spherical mirror. It looks good, until you try to draw a ray from the tip of the candle flame, then through the focal point, $F$, and then ...
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Fabry-Perot Interferometer

let's consider a Fabry-Perot interferometer: Illumination is provided by a diffuse source, and its rays are focused towards the cavity by a lens. Inside the cavity there are multiple reflections and ...
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Actual meaning of refraction of light

The definition of refraction which I found on wikipedia is In physics, refraction is the change in direction of a wave passing from one medium to another or from a gradual change in the medium. ...
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Optical shift in a view from above

In the following case, two objects are moving to each other from two different media: Apparently, the distance between the two, at this moment, is not the sum of $6$ and $0.8$, but involves dividing ...
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What role does bulk of a prism play in dispersion?

I know that a prism deviates light because the refractive index of glass is a function of the wavelength of light used. However what role does bulk of the prism play in dispersion? i.e only the ...
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What do we actually mean by parallel rays when talking about reflection from a concave mirror?

If we place a point object at the focus of a concave mirror, we say that the reflected rays would be parallel and would meet at infinity to form an image. What does this mean? I tried to trace the ...
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When parallel light Ray's ( not parallel to the principal axis) pass through a convex lens, where does it converge on the focal plane?

I know that the Ray's will converge at the focal plane. But how do we calculate exactly where it will strike? Is there any formula for the same?
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How can we apply lens makers formula to combination of lenses?

Like in lens makers formula the material must have same material on both sides but that doesnt happen when lenses are touching each other. So how can we neglect that connection and use formula as if ...
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Difference Between Angular Resolution and Spatial Resolution of optical device (Camera)

As per wikipedia angular resolution is the ability of device to capture minute details of an object and is the same definition in case of spatial resolution. Whats the difference Between Angular ...
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Reflection off of reflections in silvered glass slabs

Our instructor told us about this phenomenon: The back of the glass slab is silvered, and M' is the front-shifted image of the silvered surface. While explaining reflection off of this, he stated the ...
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Problem with Cartesian sign convention for geometrical optics [duplicate]

This confuses me a lot. We use the convention in the derivation of thin lens formula and mirror formula. In derivation in place of u (object distance) we write -u. Since we have written it this way, ...
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How a image formed by circular glass slab?

Take a circular glass slab, and mark something on a curved side, now see the image of the mark from opposite side of the slab. I observed that it is magnified, why is it so? In this, only one ...
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Can we use regular glasses with inlaid display to display images to a wearer?

Object (virtual) (distance: d) <---> Glass with some display + Human Eye Would it be possible to display something onto a regular glass covered with a ...
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A light ray grazing over a spherical material

If an incident ray just grazes over a sphere of refractive index '$n$' then will it suffer any deviation or not? According to my reasoning it shouldn't suffer and deviation as the the ray will be ...
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Real versus Virtual images: Multi-Lens systems

So I am confused about whether the final image produced by a multi-lens system is virtual or real. Is it just if that if the final image has light rays converging to that point then its real? or is ...
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What causes this circular reflection to form?

Holed up at home, I was distracting myself by shining my green laser pointer around. Something particularly interesting happened when I pointed the laser at a reflective black plastic surface. The ...
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Does a Michelson pattern have a maximum radius?

I'm studying the Michelson interferometer interference pattern and we have arrived in class - using some aproximations - to some expressions which state a relationship between the radius of the ...
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Calculating the reach of a planet's umbra

I'm trying to calculate how far behind a planet its umbra reaches. So far in my search of the topics on google I have only found pages about how to calculate the size or time of moon eclipse. But it'...
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Does the far point change while using convex lens to correct hypermetropia?

Let use create a context first: A healthy eye has horizontal range of vision from 25 cm (near point) to ∞ (far point). A person X has myopia, so his range of vision with unaided eye will be 25 cm ...
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Field curvature: why is it a third order aberration?

I am trying to understand the different kinds of aberrations that exist with rotationally symmetrical optical system, as a simple lens for example. What I have learnt so far (correct me if I'm wrong):...
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Visualisation of asymmetric placement of an object between two inclined mirrors

Suppose two mirrors are inclined at an angle $x$ such that $n = 360/x$ is an odd integer. If the object is at the angle sector then the number of images is $n-2$, I found the diagram for this case ...
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In phase contrast microscopy, how does the phase difference between the diffracted light and the background light come to be?

Phase contrast microscopy works by exploiting the phase difference between two paths of light which pass through a probe point of a specimen: One path, the "background" path, is the path the light ...
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Interesting generalisation about a parallel ray between 2 mirrors

I have been self studying from home nowadays and came across a result in a video lecture on 'Ray Optics' If an incident ray is parallel to one of the 2 mirrors kept an angle $\theta$ = $\frac{\...
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Ametropia correction

In Myopia(Near-sightedness), A concave lens is used to diverge the rays from an object and ultimately the eyes make them converge at the retina . The rays after diverging appear to converge ...
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Does Helmholtz reciprocity holds for partially coherent lights?

Helmholtz Reciprocity describes how light sources and sensors are reversal to each other. In other words, "If I can see you, then you can also see me." My question From Wikipedia's derivations, it ...
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Refocusing light field images via Fourier Slice Photograph theorem

I am trying to refocus images from a microlens array light field using Ren Ng's Fourier Slice photograph theorem found in his thesis chapter 5, equation 5.7, which is available at https://stanford.edu/...
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What is the Fraunhofer diffraction pattern of a circular aperature with a rectangular obstruction?

Suppose we have a circular aperture of radius 3$\lambda_0$ and we place a vertical rectangle of width $\lambda$ over the center of the aperture (as shown in the picture). What will the Fraunhofer ...
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Why are very thick soap bubbles colorless?

Is it simply because the wavelength where constructive interference occurs gets to be too long?
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Etendue of the eye

I am tasked with calculating the Etendue of an eye with the given values: diameter of the pupil = 4 mm diameter of the retina (the active area) = 6 mm distance from the lens to the retina (b) = 20 ...
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Chromatic aberration in lenses

We all know that concave lenses act as diverging lenses, but while searching for remedies for chromatic aberration, I observed a concave lens (in the picture see flint glass) acting as a converging ...
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Are confocal microscopy and f-number based on the same principles?

We use a small pinhole in confocal microscopy to block out-of-focus rays, much like having a high f-number (small aperture) in a normal camera. Are the two related? And does one ever tune the pinhole ...
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Two positions of the convex lens for a fixed object-screen separation

Explain why, for a fixed separation between the object and the screen(i.e., d + d' is fixed) there are two positions of the lens at which the images formed on the screen are in focus (clear images or ...
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Why does a pinhole create an image of the Sun?

When I was a kid I happened to encounter a solar eclipse. I was taught that I should not look at the Sun directly when it is undergoing an eclipse, but I was extremely curious to see it. Somebody ...
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How to think about virtual images?

I have been messing around with magnifying glasses recently and I am stuck on a simple concept. From the thin lens equation we know that $$\frac{1}{s_0}+\frac{1}{s_i}=\frac{1}{f},$$ with the sign ...
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How to graphically determine equivalent focal length of two thin lenses?

Suppose we have the schematic above. The first lens has a focal length of 80mm and the second one has a focal length of 60mm, and both are biconvex. My job is to determine, graphically the equivalent ...
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How to use convex lens to magnify image without inverting

From my knowledge, convex lenses magnify and invert light rays that pass through it. So is it possible to use a second convex lens to make the magnified inverted image into a magnified upright image?
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Mirascope Holograms

So I just realised that 3d hologram fan projectors are now a thing, and the quality looks quite good (search Ashata 3d hologram fan projector). However, an inherent problem with them is that the image ...
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Is it possible to change the location of a virtual image without using moving lenses?

The benefit of a head-up display is primarily in reducing the time required by the user to refocus their eyes from the head-down display to the head-up surroundings. In applications such as cars, the ...
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Helmholtz's Equation in Geometrical Optics

As in BSc. Physics Course, I read about the Helmholtz's equation which is as follows, $$n_1h_1\tan(\theta_1) = n_2h_2\tan(\theta_2) = H$$ in geometrical optics in the thick lens combination. Here $...
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Requirements for rays to converge exactly at a point $P'$

I am currently studying Modern Optical Engineering, fourth edition, by Warren Smith. The textbook says the following: In Fig. 1.10 several ray paths have been drawn for the case of a converging ...
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Image plane, camera location and real distance

Suppose I have a situation as shown in the image bellow. A 3D-Object I want to project into a 2D-Image with respect to the real distance. But I don't really understand the connection between the ...

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