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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Bending of light

Why does bending of light(diffraction) occur?
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Do light waves precisely follow null geodesic paths in General Relativity?

In special relativity one may show that a plane wave solution of Maxwell's equations (in a vacuum), of the form $A^a=C^a\mathrm{e}^{\mathrm{i}\psi}$ has the following properties: The normal ...
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16 views

Signal loss in non-reflected light through a tube proportional to square of the length?

Reading a patent I came across the claim: "...a portion of light intersecting the inner metal surface is not reflected, resulting in a loss in signal intensity... the signal loss is proportional to ...
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3answers
152 views

Shining a laser onto a mirror

Theoretically, if I shined a laser at a mirror at an angle of 0 degrees so that the light was perfectly reflected back to the light source, then I should not be able to see the light because it is not ...
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43 views

Why do you need at least two rays to form an image?

Why isn't enough one light beam to form an image in your retina for example?
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Using thin needle for object and thick needle for image

I have performed an experiment to determine the focal length of a concave mirror in my school lab. It consists of an optical bench with two needles, one as object and one image. We basically try to ...
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31 views

Sign convention in geometrical optics

This is slight misconception that has bugged me. While deriving the mirror formula: $$\frac{1}{u}+\frac{1}{v}=\frac{1}{f},$$ people (as per my reference book) tend to apply the sign convention to ...
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Why do we assume that rays from infinity are parallel?

If light rays are parallel to each other , if they are from infinity, they are not gonna make an image because they won't intersect with each other. So we are not gonna see the image. Does that means ...
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207 views

Infinite total internal reflection

Suppose that I have a block of some transparent material, glass, for instance, with a certain index of refraction. Suppose that the transparent material is placed in air or in any other transparent ...
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29 views

How do we call in English scientific terms the Fermat's principle about back and forth light traversal?

We know that the path followed by the light from point A to point B is independent of the direction of propagation of light. This is what is called in French "le principe de retour inverse de la ...
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21 views

Total number of primary maxima in diffraction grating

I am trying to determine the total number of primary maxima that can be observed when light of wavelength 500 nm is incident normally on a diffraction grating, with the third-order maximum of the ...
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Can focused light be treated as a point source?

Imagine there is a uniform, collimated beam coming from a distant light source. This beam passes through a lens and is focused to a point at the focal length. Can this "point" be treated as a point ...
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Calculating angle of refraction of water in this lab setup? [closed]

The setup of the experiment is as drawn in the picture (where the red circle is a rotating disk, the box is a laser and the straight line the laser beam and the semi circle in the middle of the ...
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487 views

Finding the illuminance from a triangular light source

Since most light sources in games are point-like, it's pretty difficult to approximate area light sources with point sources. As triangles are a universal form to represent 3D models (thus area light ...
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34 views

Derivation of the formula related to number of images?

I have read in my book that if two mirrors are inclined at an angle $\theta$, if 360/$\theta$ is even , the number of images is given by (360/$\theta$) -1 What is the derivation of this formula? I ...
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Do people wearing glasses have different field of view than those who don't?

There is one thing I sometimes wonder about ever since I was a child. Do people who wear eye glasses see objects in different size than those who don't?(Technically different size means different ...
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1answer
21 views

Light and Visibility [duplicate]

It is difficult to see through a closed glass window from the inside of a well lighted room, when it is dark outside. However it becomes relatively easy to see outside, when the light in the room are ...
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298 views

What determines the sharpness of a shadow?

What are the factors that affect the sharpness of a shadow? I would think that the distance between the light source and the object, the distance between the object and the shadow, and the size of ...
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35 views

Which Method for finding velocity of an object in the mirror is correct? [closed]

My Professor asked a question, "A person is seen jogging in a rear view mirror of focal length $1$m. He is at a distance $39$m from the mirror. His jogging speed is given to be $5 \frac{m}{s}$. ...
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48 views

How to determine the radius of curvature of a convex lens?

Suppose there is an equi-convex lens made of glass which has a focal length ($f$) of 30cm. Then, can we not say that the radius of curvature, $R$ of the lens is twice the focal length, i.e. $R = ...
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What is the distinction between a “ray” and a “wave” in optics?

What is the distinction between a ray and a wave in optics? From what I can gather, the only discernible difference is in nomenclature, where a ray simply refers to an EM wave with short wavelengths. ...
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193 views

Rayleigh-Plateau instability and optic [closed]

Let a liquid jet fall onto a surface. If the contact point is illuminated by a lase beam, rings of light around the jet can be observed . (pic.1) and we know it that the reason of this phenomenon is ...
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1answer
151 views

Issue on sign convention with optics

I have a problem understanding the sign conventions used in the equations that describe the imaging properties of mirrors - in particular, when and why should I use a positive or negative number for ...
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1answer
186 views

Does sign convention in geometric optics fail to explain the cases of image formation by virtual objects?

Here is an example of Cassegrain telescope: Parallel rays from a distant object get reflected by the concave mirror forming an image at its focus behind the convex mirror. This image acts as a virtual ...
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The image of an object through a curved surface

We have a curved surface, separating two different medium, with refractive index n1 and n2. We know the radius R of the curve,then how can we find the position v of the image? I read that the ...
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5answers
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Is it possible to start fire using moonlight?

You can start fire by focusing the sunlight using the magnifying glass. I searched the web whether you can do the same using moonlight. And found this and this - the first two in Google search ...
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Rings of light around a jet [duplicate]

When an obstacle is put in the path of a liquid jet, some standing waves are created upstream of the obstacle (see the pic) or we can say a similar form like this for them ( the wavelength of ...
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2answers
129 views

Why doesn't a Gaussian beam converge to a point?

No matter what lens is put in the beam path of a Gaussian beam, it will always go through a waist of non-zero width. Why not just a point? I know the maths, I'm wondering whether there is any ...
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Confusion with Fermat’s principle of least time [closed]

Here is an illustration used in my book to prove format’s principle of least time. My book says that ACB will be the shortest path. It is obvious that light reaches E first, and then X. If the ...
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Prismatic shaped rear view mirrors

To reduce the intensity of the incident light, prismatically shaped rear view mirrors are used in cars with a day-night switch which changes the angle such that instead of the polished surface ...
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2answers
661 views

Magnification in compound microscope

I was studying about compound microscope here I don't see why we multiply linear magnification of objective with angular magnification of eyepiece. Shouldn't it be both angular or both linear? Can ...
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40 views

Lens formula and Lens maker's formula

When we derive the formula for lens and lens maker's formula using the formula for refraction at spherical interface $$\mu_2/v - \mu_1/u = (\mu_2-\mu_1)/R$$ we put $u$ to be $-u$ as it is on the left ...
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67 views

Combination of mirror and lenses [closed]

I am a keen learner of physics, but I am unable to solve problems involving lenses and mirrors together. please can anybody tell me the method to solve these problems? for instance let us take a ...
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31 views

Refracting telescope image formation

I'm having some trouble understanding how a refracting telescope forms a magnified image for an object that is not assumed to be infinitely far away. I drew this ray diagram: And as you can see, a ...
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pinhole in projector screen

Consider a conventional slide projector projecting a properly focussed static image from a photographic slide onto a conventional screen, with a second screen placed a short distance behind that one. ...
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Image formed by a Prism

A series of questions that came in my mind after I saw a question So here it goes first the questions that have made me confused : 1) How image is formed by the prism? 2) When we take different ...
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2answers
52 views

Are these reflected rays really parallel?

I have read that if an object is placed on the focus of a concave mirror (assume that the object is a vertical line placed on the focus), then the image will be formed at infinity. Here’s a diagram. ...
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Experiment to find the circle of least confusion (optics)

I want to conduct an experiment where the circle of least confusion (wiki ref) occurs for a lens. Suppose that I shine white light onto the lens and I know the lens EFL is lets say 100 mm, in order to ...
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716 views

Highly diminished image of an Object placed at Infinity

Consider an object at infinity. The rays coming from it are parallel to each other. Let one of the parallel rays pass through the focus $F_1$ of a thin lens, and let a second ray pass through the ...
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1answer
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Do all thermal radiators have the same surface brightness?

Imagine I heat a piece of metal to 1000K. It will be red hot and will emit black body radiation corresponding to this temperature. But what about the brightness? Assuming the bulk is opaque, does it ...
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Software for geometrical optics

Is there any good software for construction optical path's in geometrical optics. More specifically I want features like: draw $k \in \mathbb{N}$ objects $K_1,\dots,K_n$ with indices of refraction ...
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100x magnifying optics system for short laser pulse

I am now designing an experiment that consists of a 400 nm short pulse (~300 fs). In the experiment, we need to magnify the transverse profile of the pulse by 100x. That's the problem. I was ...
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Balance lens tilt aberration

Given a doublet (singlet in reference figure), if the rays enter at an angle with respect to the origin axis, we would see a shift of focal length for blue and red. A known optical jitter How could ...
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1answer
135 views

Blonde hair looking green at certain angle

I have a friend who has blonde hair. And when look at an oblique angle, there's a tinge of light green in her hair. I've heard that the copper ion in pool water can make blonde hair green, but her ...
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Let's suppose I am to display the letter R on mirror as well water , will I get the same images?

As far as my practical experience goes both look quiet the same when an image of any object is formed on them, yet I wanted to be ascertained is there any actual visible differences between both the ...
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Encoding multiple images in 1 beam

I am doing some research involving geometric optics. I need to reduce an image in size so it fits a rotating mirror we are using. I came up with the idea of projecting the focal plane on the mirror, ...
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Why to use the sign convention while solving problems as the mirror-formula itself is derived using the sign convention? [duplicate]

When we derive the mirror equation of concave mirror, i.e.,$\frac{1}{u}+\frac{1}{v}=\frac{1}{f},$ we've already used the sign conventions. Then why to use the sign conventions again while solving a ...
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45 views

Velocity of image formed by a spherical mirror in Y axis

If an object is moving with velocity $v_0$ along the positive Y axis in front of a convex mirror of focal length $f$ at a horizontal distance $u$ from the mirror's pole, what will be the velocity of ...
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Examples in which the light maximizes the optical path length

I posted a similar question about geodesics on Math.SE. Many sources (Wikibooks for instance) claim that the light could maximize the optical path length in some cases. But I don't think it's actually ...
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2answers
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How does Huygens Principle incorporate the unidirectional property of a traveling wave?

I was reading French's Vibrations & Waves where he discusses Huygens-Frensel Principle. The principle talks about how secondary sources give rise to secondary wavelets to form the displaced ...