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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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 ...
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1answer
28 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 ...
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1answer
35 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?
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1answer
28 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?
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16 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 ...
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2answers
40 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 ...
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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 ...
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1answer
35 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?
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1answer
779 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 ...
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27 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 ...
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59 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 ...
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2answers
38 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 ...
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37 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 ...
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1answer
92 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.
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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?
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2answers
47 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 ...
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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 ...
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2answers
53 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 ...
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1answer
67 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 ...
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0answers
25 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 ...
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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. ...
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268 views

What is the physical meaning of magnifying power of a telescope?

So the following question was given in the JEE Mains 2016 conducted throughout India on 3rd April. An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20. To ...
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0answers
24 views

Is it possible to use a tapered fiber to collimate a single-mode light beam?

I would like to collimate a light beam stemming from a single-mode LED source. As the source is pretty big (a few millimeters), collimation with a single lens gives a bad result, i.e. a quite ...
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1answer
62 views

Why does a specific static image “move” when moving my head? (glass user)

I am a daily PC user. As most users, I have a taskbar (using Windows) that shows icons of programs. My two screens are big (24") and I'm at ~60cm distance from them, so fairly often I need to turn my ...
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1answer
33 views

Attenuation of light through a simple lens, and is it important?

I have an object with incident light rays traveling away from this object. Some of these rays are traveling from the left-hand side through a simple lens (say, a double-convex converging lens). As ...
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2answers
93 views

Why is this laser beam being scattered(and not)?

I was shining a laser beam through a liquid filled test tube(an ester particularly),and I found this phenomenon rather intriguing.Have a look. Now when I passed the laser straight through the ...
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2answers
74 views

What is exactly an ‘virtual object’ ? ( From the point of view of lens maker’s formula )

Here’s an image from my textbook It shows, how an image is obtained from a convex lens. The second and the third images, shows in depth , that how a convex lens behaves. They say, that suppose ...
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1answer
23 views

Why should the ray become parallel to base in a triangular prism at minimum deviation?

In the case of minimum deviation, the refracting angles at two surfaces are equal. Then the ray inside the prism should be parallel to the base only if it is isosceles triangular prism. But everywhere ...
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2answers
52 views

Magnification vs Magnifying Power [closed]

I've read it a lot of times. But I've not been able to get around magnifying power and magnification of a simple microscope and the difference between them. Can someone explain?
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1answer
49 views

Deep confusion with conventions and signs in geometric optics

This is an equation given in my book. The question is why have they used a negative sign on the LHS? Now, if you try to derive the mirror equation with simple geometry, you get 1/v +1/u =1/f . ...
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21 views

Plotting EM fields

I am currently studying transformation optics and learning about electromagnetic cloaking. To plot my results(Electric and magnetic fields) i have to solve maxwell's equations given the permeability ...
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3answers
24 views

What is the meaning of size of the image?

Say I am standing at a distance of $20m$ from a plane mirror and looking at it. My image in it as I see it is smaller than how I perceive myself. Why then does my physics textbook tell me that in a ...
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4answers
31 views

Light field 5D Plenoptic Function

Wikipedia says "Since rays in space can be parameterized by three coordinates, x, y, and z and two angles $\theta$ and $\phi$, as shown at left, it is a five-dimensional function" I'm not ...
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2answers
56 views

Shape of a mirror that focuses non-parallel light

If I am not mistaken, a parabola is the shape that a mirror has to be to focus ideal, parallel light rays to a single point. Real light sources are usually not actually parallel though, but are more ...
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36 views

Concave lens path of ray

What will be the path of ray passing through the first focal length of a biconcave thin lens kept in air? I know that a ray passing through focus or appearing to pass through focus of a thin lens ...
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2answers
55 views

The image of a wall clock is to be obtained on the opposite wall 2m away by the means of a convex lens. What is the minimum focal length required? [closed]

I'm in 10th grade and this question came in my physics test. Nobody was able to answer this question correctly except my physics teacher who says that the answer is 2m. My answer is that there should ...
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2answers
48 views

Reflection law (from Fermat's principle) for arbitrary surface

Normally reflection law is deduced from Fermat's principle (e.g. here) for a planar mirror. Also some other mirror surfaces can be studied (e.g. here they treat a spherical mirror). Is there some ...
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44 views

How to solve this problem : A glass sphere of radius 1 m and refractive index 1.5 is silvered…? [closed]

Problem: A glass sphere of radius 1 m and refractive index 1.5 is silvered at its back. A point object is kept at a distance of 1 m from the front face, as shown in the figure. Find the position of ...
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3answers
81 views

Application of Snells law

What i know about snell's law: It is applied when a ray of light meets the interface of some other medium and we can find the fourth quantity if we know any of the three quantities in the following ...
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1answer
23 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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2answers
101 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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3answers
62 views

Bending of light [closed]

Why does bending of light(diffraction) occur?
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20 views

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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1answer
33 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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1answer
131 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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1answer
50 views

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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2answers
94 views

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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0answers
67 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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1answer
25 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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62 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 $5 \frac{m}{s}$. ...