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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2
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2answers
68 views

What is the optimal distance to sit from a TV? [on hold]

I was wondering how to calculate the optimal distance to sit away from a TV. I don't quite know the full set of parameters it will depend on, I would suspect it to include the following: Size of the ...
3
votes
0answers
88 views

Optics: finding total power of a system, including wavelength

Specifically I need to create an ABCD matrix given 2 radii of curvatures, the thickness of the lens, type of glass (BK7) and a given wavelength. I will have to figure this out eventually, so help ...
40
votes
5answers
5k views

If a lens focuses all incoming light to a point, how do we get 2D images?

How do lenses produce 2-dimensional images, if a lens bends all incoming rays of light to intersect at the focal point? Shouldn't this produce a single dot of light on a screen placed at the focal ...
1
vote
0answers
24 views

Analytical calculation for focus deviation [on hold]

How can I analytically calculate the deviation in focus or focal length variation in a situation as shown in figure. When the Sensor is parallel to the face of the lens/ light; its easy to calculate. ...
-2
votes
2answers
59 views

Can we take photo of a mirage? [closed]

I do know that mirages are optical illusions . I know the phenomenon of its formation just tell me if we can ?
0
votes
0answers
20 views

Difference between linear magnification, axial magnification and aerial magnification (w.r.t. mirrors)? [closed]

Please explain how the three types are different from each other using pictures (preferably) or diagrams. And if possible, an explanation regarding how each would be different for mirrors and lenses ...
1
vote
1answer
39 views

Question about Fermat's principle

Why when deriving the law of reflection from Fermat's principle of least time do I set $dL/dx = 0$? I am a 12 grade student with a little notions of maxima and mimima in one variable calculus.
0
votes
3answers
67 views

what is the purpose of condenser lens in a slide projector?

What if we don't use any condenser lens? can't we use a single convex lens as a condenser? what difference will it make? kindly explain it in detail.
0
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0answers
23 views

What is the purpose of condenser lenses in the slide projector shown below? [duplicate]

I searched a lot on internet about this.I could not find the working of these condenser lenses in detail. Some websites say that condenser lenses make the light rays parallel and to pass through ...
0
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0answers
15 views

opaque to transparent based on distance of object?

If we look through a transparent glass window of an apartment, from a distance in day light, we can’t see what or who is inside. All the light is reflected off the surface of the transparent glass ...
-1
votes
0answers
15 views

How to converge two independent point light sources with a single biconvex lens (20D)

I need to take an image of fundus of an eye. So I'm using a 20D lens to see the fundus. Camera is kept in the same axis and eye is illuminated by two 3v LED's. The LED's are placed just at the edges ...
5
votes
0answers
35 views

Does the curvature of the IMAX screen improve the view of 3D video projections in any way for viewers not sitting in the “sweet spot”?

When I think about a simple 2D projection on a screen with vertical-cylinder curvature and of viewing positions away from the "sweet spot" it seems to me pretty obvious that there would be geometrical ...
3
votes
2answers
532 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 ...
1
vote
1answer
41 views

why can't we see our image on a simple brick wall?

We can see our image in a mirror due to the reflection of light. We also know that a red color brick wall also reflects light. So, why can't we see our image there?
2
votes
2answers
3k views

Huygens' Principle During Reflection: comparing wavelets from before reflection with wavelets from during reflection

I was recently reviewing geometric optics, during which I read about Huygens' Principle and how it could be used to prove the Law of Reflection from the "light is a wave" viewpoint. I'll quote what I ...
0
votes
0answers
30 views

What is the angular dispersion of an optical surface grating and why does the textbook answer seem to violate reciprocity?

The behavior of a surface grating can be described by the grating equation $m\lambda=d(\textrm{sin }\theta_i+\textrm{sin }\theta_d)$ [1] with $m$: diffraction order, $\lambda$: wavelength of the ...
1
vote
2answers
52 views

Lensmaker's equation and Imaging properties

In the textbook, usually the following construction (see the figure below) is used to determine the relative size of the image and the object. I understand that a ray parallel to the optical axis ...
0
votes
1answer
156 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 ...
3
votes
2answers
857 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 ...
2
votes
2answers
56 views

Why don't reflector telescopes place their reflectors at an angle?

To avoid placing a secondary mirror in front of the objective mirror, why not tilt the objective and design the eyepiece in such a way that comatic aberration is minimized?
-1
votes
0answers
14 views

Refraction in solutions [duplicate]

What is significance of dn/dc change in refractive index over change in concentration of the graph of refractive index against concentration of a solution
1
vote
0answers
25 views

How is the Rayleigh criterion connected to the Abbe limit

I am interrested whether one can derive a formula for the point resolution (like Abbe did) of an optical system from the Rayleigh criterion (without the use of small angle approximation i.e. $\rm{sin}(...
0
votes
0answers
9 views

Coordinate Equation of a curve which bends all the parallel incoming rays from infinity towards a single point

How should i proceed on to find the coordinate equation of a curve such that it bends all the parallel rays coming from infinity towards a single point. Yes I know that it would be a 2nd degree ...
3
votes
1answer
39 views

Relationship between angular magnification and how much bigger the image appears

How is the angular magnification of a magnifying glass related with how much bigger the image appears to the user? Is it simply the same? If yes, why? (Let's assume that the object is placed in the ...
1
vote
1answer
40 views

If I placed a converging lens in water, would its surface power change?

If I placed a converging lens in water, would its surface power change ? The first case when the lens is in air then placed in water; does the surface power change or remain the same?
1
vote
1answer
64 views

Why should the image screen be placed at fourth focal plane in 4f setup?

They call it the 4f setup. But when the image coming from the second lens is anyway collimated, why is it necessary to place the image screen at the fourth focal plane?
5
votes
1answer
207 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?
1
vote
2answers
888 views

How second image is brightest here?

One of my Textbook's Multiple Choice Question is- A Thick plane mirror shows a number of images of the filament of an electric bulb. Of these, the brightest image is the- First Second Last Fourth ...
0
votes
0answers
31 views

Sun light collimation

Is it possible to make sun light collimated in such a way, to increase energy density and keep it more less parallel? like on the Earth we have intensity of sun approximately 1300 watt/m2. If we use ...
0
votes
2answers
49 views

Explanation of ray caustics in E&M

My understanding (now) of a real caustic is that it is envelope of curves or ray-paths that arise due to reflection or refraction from the medium/manifold. My main question is, I am seeing the term "...
0
votes
1answer
41 views

Which shape focusses rays to a single point?

Which shape after refraction concentrates monochromatic light rays parallel to a single focal point at origin inside a denser medium like glass?
0
votes
0answers
19 views

addition of two lenses with a finite separation in between

Suppose there are two lenses with focal length $f_1$ and $f_2$ respectively. The effective focal length $f$ when they are combined is $1/f=1/f_1+1/f_2$, but this formula assumes the separation between ...
6
votes
4answers
10k views

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 $...
13
votes
1answer
787 views

Reflection of light rays

A set of light rays emitted from a point of an orange hits a smooth and flat surface. My question is: The angles of incidence are different, light rays are reflected towards different directions, why ...
2
votes
0answers
62 views

Breakdown of Snell [closed]

I have reason to believe the following: If we are using an accurately formed thin prism, with an apical angle of let's say 2 degrees, and direct a monochromatic source beam thru a slit onto the ...
1
vote
1answer
29 views

Actual spot size = geometric spot size + diffraction spot size?

I read in [1] that for a camera obscura the total spot diameter is equal to the diameter of the spot produced concerning geometric optics only plus the diameter of the spot concerning only diffraction....
2
votes
2answers
43 views

How does change in medium affect object distance/image distance?

Say,we have a container filled with a liquid of refractive index $7/5$ upto a height up $H$. There exists a plane glass mirror at the bottom of the container. Now if a fish were placed at a height of ...
0
votes
2answers
1k 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 ...
0
votes
1answer
38 views

Focal Length Calculation [closed]

Although I research in the internet, I couldn't find detailed answer. I have a question and I want to make sure from the answer. The ligth is coming from a fiber laser source and focused on a ...
3
votes
2answers
58 views

Optics to correct focal distance across a plane

I have a laser beam which is focused to a point at a certain distance. I'm then going to use a galvanometer to scan that beam across a plane. Obviously, as the beam scans across the plane, the ...
-5
votes
1answer
95 views

Does this picture look wrong to anyone else? [closed]

There is a typo. One which obfuscates the main point and makes it difficult for anyone unfamiliar with the problem to deduce the answer.
0
votes
1answer
23 views

Minimum deviation of prism

Is it right to say angle of minimum deviation of a prism is an arithmetic mean of incident angle and emergent angle?
0
votes
2answers
51 views

Definition of a ray?

The typical definition of a ray and the one that I was initially taught was that a ray was a line perpendicular to the wave front. However, when reading up on birefringence it seems as though there ...
0
votes
1answer
18 views

Power distribution in a defocused focal plane

Given an optical system of focal length $EFL$ and f number $f/n$, if the focal plane is defocused in a way that the defocused plane distance from the focused plane is $d$, assuming we have a point ...
2
votes
1answer
69 views

Would the moon be brighter if it were completely spherical?

I remember reading Galileo's 'Dialogue Concerning the Two Chief World Systems' where Salviati and Sagredo explain how the moon would be almost entirely dark if it were a perfect sphere but after ...
3
votes
0answers
30 views

Where do rays that are not marginal or principal get stopped?

The picture is from an MIT lecture but the concepts are explained in many optical texts. The chief/principal rays go through the center of the aperture stop, hit the edge of the field stop, and the ...
6
votes
1answer
305 views

Reconciling total internal reflection and the evanescent Wave

I understand that light is guided in a dielectric waveguide via total internal reflection. My question is regarding the origin of power contained in the evanescent field traveling along the direction ...
4
votes
3answers
4k views

How to make the projected image smaller by adding one ore more lenses in front of the built in projector lense?

I have a projector that creates a large image, even if the distance to the screen is short. The device is very small, approximateley 10x10 cm if you look from above. The height is only 3 cm. I ...
2
votes
2answers
107 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?
0
votes
0answers
20 views

Geometric optics, the size of the image

I have the following question from Snell's Law, I calculated the apparent location of the light source by: X = 20/1.47 = 13.6 So, this should be the apparent location of the light source. ...