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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Is it possible to build an optical system that increases the perceived surface brightness?

So is it possbile to build a system from lenses and mirrors that can make faint gas nebulas brighter or can be used as nightvision? If you increase the size of the aperture of a telescope it will ...
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1answer
146 views

Image formed in a compound light microscope

I am trying to understand whether the image formed in a compound light microscope is at infinity or not. I get conflicting answers everywhere I look.
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3answers
392 views

Reflections in Rearview Mirror

Why is it that in the reflection in the rear view mirror of your vehicle in the car behind you The driver is on the drivers side and the passenger is on the passenger side and when they raise thier ...
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1answer
67 views

Why is there no dark band below a rainbow?

I've read articles about Descartes' theory of the rainbow and I can understand why there is a dark band of about 8 degrees (Alexander's band) between the primary and secondary bows: for all the water ...
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377 views

how does the mirror equation works and what lead to using of sign convention?

EVERYTHING HERE IS FOR CONCAVE MIRROR Everywhere I see the derivation of the mirror equation is given by placing an object before the focus and then proving similarity of the triangles to get to the ...
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173 views

How many mirrors placed perpendicular to each other shall make a light ray completely reverse its path?

The answer is 3. But according to me 2 shall also work in 2 Dimensions? Does anyone has a theoretical proof?
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194 views

How to determine if a optical system is afocal?

I have to come up with a method to measure the focal length of a concave lens that's not in my lab guidebook. So I decide that I will build an afocal system with a convex lens and a concave lens and ...
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157 views

Infinite Mirror Face to Face With Infinite Two Way Mirror

If you are in deep space, and there is an infinite plane mirror, and in front of it there is another infinite mirror that is two way, with the see through side towards you, what do you see? Is it the ...
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156 views

Refraction of light in medium

Given that the plane $y=0$ separates the vacuum ($y>0$) from the optical medium ($y<0$), I would like to calculate the trajectory of a light ray starting at the point $(x_1,y_1)$ and ending in ...
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Why Does Passing Light Through a Slit Make it Coherent?

Related: Why incoherent source of waves have to be passed though a single slit for double slit interference pattern to occur? If you have a an incoherent light source, why does passing it through a ...
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1answer
190 views

Optical Waveguide's “Base Bandwidth”

Consider a dielectric slab waveguide (lossless, isotropic) illuminated transversally from the vacuum (with coherent, monochromatic light). We define the base bandwidth of a waveguide (or optical ...
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120 views

How is Fermat's least time principle proven?

How is Fermat's least time principle proven? Or it is what usually is observed and is basis for the theories?
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1k views

Analytic solution for angle of minimum deviation?

Consider a simple prism with a prism angle $A$, angle of incidence $\theta_1$, angle of emergence $\theta_4$ and the first and second angle of refraction as $\theta_2,\theta_3$. the refractive index ...
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255 views

Refraction Vector (Ray tracing)

I am doing ray tracing and I do the refraction of the ray using the following relation (I got it from PDF called "Reflections and Refractions in Ray Tracing"): But I have seen it in another PDF as ...
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103 views

Lenses and Magnification [closed]

A $2.05\text{ cm}$ tall object is placed $30.0 \text{ cm}$ to the left of a converging lens with a focal length $f_1 = 21.0\text{ cm}$ . A diverging lens, with a focal length $f_2 = -42.5\text{ cm}$ , ...
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2answers
128 views

Good explanation of a real image?

Okay well I've started to study phys chem in school recently and I honestly can't get my head around what a real image actually is I've asked my teacher to demonstrated it but she's quite lazy, and ...
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2answers
206 views

Calculate the polarization vector on reflection or refraction from a dielectric interface

I am interested in ray-tracing polarized photons. I have code that works very well for unpolarized light. When a ray hits a dielectric interface the photon is either reflected or refracted by ...
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2answers
155 views

Change of hue near shadows

My brother is an artist and he told me his paintings look more natural when he slightly change the hue (color) of the surface near the transition between shadow and light. Here's three examples: (1) ...
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2answers
723 views

Why do powers of lenses get added?

In our physics class, we were told that a power of a lens is defined as the reciprocal of its focal length. Also, the powers of multiple lenses get added up. But I didn't understand why this is. I ...
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204 views

How mirror equation can explain farsightedness correction?

I have a friend who has just show me his medical prescription for hyperopia (farsightedness) correction and he needs glasses with 4,25 diopters for that, which seemed to be weird for me because I had ...
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384 views

Wave theory limit of geometric optics? [duplicate]

Why is geometric optics the low wavelength limit of the wave theory of light? I can't seem to grasp why either a low or high wavelength limit would be necessary.
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1answer
189 views

Refraction of light in water

Here's a question in a paper based on refraction of light. I can't seem to solve it for some reason. A man looks down at a fish length of 20 cm. His eye is 2m above the surface of the water ...
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2answers
292 views

Converting indices of refraction

If I know that the index of refraction of a given substance is 1.4 for the average wavelength (say 550 nm), and I would like to know what is the index of refraction with a wavelength of 832 nm, how ...
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2answers
270 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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113 views

Simulating an Optical Lens

An optical lens focuses the light according to a rule (due to its special shape) and we know that rule. Now, instead of making bigger and bigger lenses, can we use an array of optical sensors and the ...
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3answers
531 views

Two different mediums can have equal index of refraction?

In other words: given a certain medium, is light's phase velocity unique?
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40 views

How close do two wavelengths of light need to be to produce a metamer?

Suppose I have two wavelengths of light ($r_1$, $r_2$) coming from a source. These rays are then reflected specularly on a surface. What is the minimum distance required for the two wave trains of ...
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148 views

Formation on image on screen?

When we first learn elementary geometrical optics, the first thing taught to us is the two broad divisions of the type of reflection.-Regular and Irregular or Diffused. The difference in cause for ...
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120 views

Seeing the image as explained by Geometrical optics?

I was thinking about how the human visual system perceives the position of an object. I assume it essentially does this by focussing the incoming rays onto the retina and then judging from the power ...
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1answer
126 views

Perfectly focusing refractive surface

On reading Feynman's lecture on physics, in the geometrical optics section he said that a curve which focuses all the rays coming from a point to another fixed point beyond the refracting surface ...
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83 views

Is my textbook in error about this geometric optics relation?

Given a centered optical system (having an axis of rotational symmetry), let $H_1$ be the intersection of the optical axis and the "principal object plane" (I'm studying in French and have no idea how ...
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518 views

Light Ray Reflection from concave mirror

Suppose a ray of light hits a concave mirror and is parallel to principle axis but far away from it such that it doesn't follow paraxial ray approximation. Will it pass through focus or between focus ...
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108 views

Is light red shifted in optical tweezers?

This is a question I put to my supervisor during my PhD many years ago, and never really got a satisfactory answer to. In an optical tweezers, assume that a beam of light is used to move a glass ...
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1answer
262 views

Why can't we see real images?

When light from an object passes through a convex lense, it gets reconverged at a single real image. From there, the light rays presumabely begin diverging again, exactly as if there was a ...
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2answers
2k views

Can virtual image be photographed

Is there any instrument that can photograph a virtal image? How would such a device work?
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421 views

How does the eye perceive a real image?

Okay, so I'm trying to grasp how the human eye will perceive the real image created for example by a convex lens. Take the upper image in this picture for example. If you were to place a screen at ...
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332 views

Why don't you see multiple images of an object?

Consider the ray model of light. Let's say an object such as a pencil is illuminated, and consider one point on that pencil. Since there could be many rays of light bouncing off the same point on the ...
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478 views

Sign convention of the lens formula and its application

Why is the sign convention used in the derivation of the lens formula and yet used again when it is applied in numerical problems? Won't the whole idea of sign convention be eliminated if it is used ...
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1answer
161 views

Which fraction of light is refracted from a source of light under a lake?

I was trying to solve this problem: "A punctiform source of light is standing inside a lake, at a height h of the surface. f is the fraction of the total of energy emitted that escapes directly from ...
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2answers
163 views

Proof that a spherical lens is stigmatic

In geometric optics, we generally allow that, for example in the case of a convex lens, rays coming from a particular point get refracted towards another particular point on the opposite side of the ...
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357 views

What does it mean that a wavevector is null?

I have derived geometric optics for gravitational waves and I am trying to interpret one of the results. I have \begin{equation} k_{\rho}k^{\rho}=0 \end{equation} for the wavevector. For the case ...
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4answers
300 views

What does the wave principle of light actually represent?

Light has a dual nature, one of photons and the other of waves. But energy doesn't really travel in waves. So what do the wave represent?
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13 views

Image formation [duplicate]

What is the real cause behind the formation of an image? It is explained as" when rays of light focus at a point image is formed." So here we have two events, one focusing of light and another ...
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2answers
522 views

All mirrors always shrink to 50% scale?

I have this geometric optics exercise here, in which a man is looking at himself in a mirror. Determine the minimum height at which the bottom of the mirror must be placed so the man can see his ...
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1answer
276 views

Eikonal approximation for wave optics. Why follow the unit vector parallel to the Pointing vector?

The description of the passage from wave optics to geometrical optics claims that light rays are the integral curves of a certain vector field (the Pointing vector direction, normalized to 1). Here ...
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2answers
640 views

Can't seem to reconcile geometric optics and wave optics

I was looking at a physics situation involving light, and I can make the correct derivation assuming light is a ray of a given intensity (geometric optics), energy conservation checks out, everything. ...
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1k views

Does light reflect if incident at exactly the critical angle?

A lot of textbooks and exam boards claim that light incident at exactly the critical angle is transmitted along the media boundary (i.e. at right-angles to the normal), but this seems to violate the ...
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187 views

On the optics of high-resolution surveillance drones

In this youtube video (which is an except from a documentation I believe) a DARPA development for a high-resolution surveillance camera is presented. This question is regarding the optics that are ...
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1answer
271 views

Thin lens formulae

Hi I have a question about applying the thin lens formula $$ \frac{n_1}{s_o} + \frac{n_2}{s_i} = \frac{n_2 - n_1}{R} \,\text{thin lens formula}$$ for a single lens emerged in medium $n_2$ in the ...
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2answers
388 views

Goldfish perspective

What does the world look like from the Goldfish point of view, from inside a spherical aquarium? If our eyes were inside, would we be able to see the straight lines, focus on different objects and ...