Tagged Questions

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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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 ...
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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 ...
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 ...
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. ...
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 ?
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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 ...
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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.
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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.
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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 ...
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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 ...
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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 ...
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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 ...
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 ...
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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?
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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 ...
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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 ...
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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 ...
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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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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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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?
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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
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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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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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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....
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 ...
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 ...
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 ...
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 ...
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.
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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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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 ...
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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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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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 ...
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 ...
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 ...