Questions tagged [lenses]

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What's limiting the field of view of a lens

An ideal lens with finite aperture leads to the formation of an image in the image plane as \begin{equation}g(x, y) = \int \text{psf}(x/2d - x', y/2d -y') f(x', y') dx'dy',\end{equation} where $g(x)$, ...
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How would the focal length of a convex lens change if it is submerged in a liquid of higher optical density? [closed]

We know that when a convex glass lens is submerged under water, it's focal length increases- As refractive index of the pair of media reduces and the light rays deviate less to meet the principal axis ...
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How the center of Newton's ring can be bright?

We all know that due to interference of light on a plano-convex lens, central dark fringe is created. Most commonly known as Newton's ring. But is it possible to create central bright fringe? How the ...
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Lens Design 60GHz Radar

I'm trying to design a lens for a 60GHz radar chip however rather than focusing the radar beam I'd like to widen it to a specific width. Also, the radar antenna has a main beam width that is larger ...
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1answer
22 views

Magnification of a compound microscope

Whilst finding the magnification of a compound microscope, we multiply the linear magnification of the objective with the angular magnification of the eyepiece. This gives us the angular magnification ...
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19 views

How the size of central maximum magnifies in presence of convex lens?

How the size of the central maximum magnifies in presence of a convex lens to f$\lambda$/a? this question is actually the extension from chat (https://chat.stackexchange.com/transcript/message/...
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Will this combination focus my image closer?

Bringing thin lens together changes their effective focal length. $$\frac{1}{f_{\text{eff}}}=\frac{1}{f_{1}}+\frac{1}{f_{2}}$$ Lets us consider a biconvex lens. If we cut it along the principal axis ...
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In Fourier Optics, does the distance between a lens and a diffraction apparatus have an impact on the shape of fringes?

In our optics lectures we were given the following explanation as to how to deal with a lens as a fourier element: We are told that to find the intensity function of the diffracted light, we first ...
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Estimate off axis source light loss with lens?

Issue: I'm trying to measure some light sources very accurately. I'm finding an issue with light detected by the camera falls off as you move off the axis of the lens. Our objects are not ideal point ...
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2answers
53 views

Why do different colors appear to move at different rates when I shift my head while wearing eyeglasses?

I have significant nearsightedness (and some astigmatism), but see just fine with eyeglasses. One phenomenon I've noticed is that when I shift my head side to side or up and down while keeping my ...
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Answer different using effective focal length of combination of lens

Q)The figure shows a silvered lens. $\mu_A = 1.6$ and $\mu_B = 1.2$, $R_1 = 80$cm, $R_2 = 40$cm and $R_3 = 20$cm. An object is placed at a distance of 12 cm from this lens. Find the image position. I ...
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Spherical Lens Instead of Parabolic Lens

I know that using the paraxial approximation, spherical lenses behave like parabolic lenses. It seems that there is no reason to use spherical lenses instead of parabolic (because they are used in the ...
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1answer
39 views

What shape lens will focus parallel laser beams to the smallest point?

I'm playing with Algodoo optics. I'm trying to focus parallel lasers using refraction. I thought an ellipse or parabola would work, but not precisely. As you can see in this picture, the ellipse ...
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$ABCD$ matrix formalism for concave mirror

I need to calculate the $ABCD$ matrix for a thick concave mirror, in the situation in which the light comes from the plane side of the mirror, and it is the concave part that is coated (for reference, ...
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21 views

Relationship between the power of a convex lens and the refractive index of a medium

According to the Lensmaker's formula, $$\frac{1}{f} = (μ-1)\left(\frac{1}{R_1} - \frac{1}{R_2}\right)$$ Apparently, focal length $f$ is inversely proportional to the refractive index of the medium $μ$....
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32 views

How do the evanescent waves contribute/cause a diffraction limit?

In the following article, under the section Physics of the Superlens, it is stated: The light emitted or scattered from an object includes not only propagating waves but also evanescent waves, which ...
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50 views

Why would a 1.74 index lens be more prone to chip and be less resilient than 1.67?

My optician counselled me I don't recommend a 1.74 index with a metal grooved frame, like the one you want from ic! Berlin, because the edge will be less resilient and be more susceptible to chipping....
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How to add Aperture stop to abcd matrix?

I want to write the abcd matrix of an optical system but I am not sure how to add the aperture stop? Given the diameter of the aperture stop and the system works on f/8. With f is the f number. Any ...
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How do I find the focal point for one lens in a double lens system?

So I'm trying to construct something that will use the two lens, (1) and (2) where lens 2 is 4x bigger than lens 1. The point of this thing will be to heat the small plate at the end of the cylinder ...
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39 views

Is it possible to focus light from a screen?

Let's define a screen as a surface emitting light in all directions. What I'm trying to find out is if there is an optical method that allows bundling the emitted light to be focused on a single point ...
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1answer
47 views

Shaped charges/explosive lenses and implosion in the Fat Man design for the Nuclear Bomb: how do these actually cause implosion? [closed]

This is gone into at some length but not much detail (that I could understand) in "The Making of the Atomic Bomb" by Rhodes. The basic story is that the Americans were having trouble getting ...
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How to calculate magnification with a lens array?

I am studying plenoptic camera, I have a simple system with a main lens, a microlens array and a sensor. I am following Hahne thesis (http://www.plenoptic.info/) and I want to calculate the ...
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Do identical, equally spaced lenses possess the same magnification, or does it depend on the sample's distance?

Do identical, equally spaced lenses always have the same magnification, or does it depend on the sample's distance to the first lens? This question comes from trying to solve: "There are 4 ...
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Problem of lens distance - Geometrical optics

I'm study geometrical optics and I'm doing an exercise which says: To the left of a thin lens an object is located at a distance p in various positions, indicated in the table. For each of the ...
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1answer
31 views

Convex Lens forming plane wavefront

As we can see in the above diagram, as we move along the symmetric axis of the convex lens, D varies. Therefore the rays coming out of the point source hitting different points of the lens surface ...
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What is the waist radius of a gaussian beam after passing through lenses with different numerical apertures?

I have a question regarding gaussian beams and lenses. If a collimated gaussian beam hits a lens with a certain numerical aperture ($\mathrm{NA}$), we can calculate the beam waist in the focus by $\...
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26 views

Focal length of telephoto lens

I am trying to use the 16mm CGL Telephoto Lens for Raspberry High Quality Camera for a microscope project and I am confused by its back focal length being 17.53 i.e longer than the 16mm focal length ...
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1answer
26 views

Can an image formed by gravitational lensing be corrected for the inevitable aberration?

Carl Zeiss would not be impressed with your average gravitational lens. Compared with familar optical lenses that are generally used to form sharp undistorted images, gravitational lenses make quite a ...
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Why do the asymptotes appear in the graph of $u$ against $v$ for the thin lens equation and what does this represent?

For the thin lens equation, $$\frac{1}{v} = \frac{1}{u}+\frac{1}{f}$$ when $u$ and $v$ are plotted to determine $f$ you get a graph like this. Why do the asymptotes appear and why can we use them as a ...
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Fresnel lens safe viewing distance

I work for a summer camp, and we have a Fresnel lens that is roughly 18in x 24in. I'm writing a safety document for the device, and am attempting to find out the minimum safe viewing distance without ...
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26 views

What is the magnification of the image produced by a convex objective lens in a refracting telescope

Let's say a refracting telescope with a convex objective lens and a convex eyepiece is viewing a distant object in space. Will the image produced by the convex objective lens be magnified or reduced? ...
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In a conventional microscope, when the spot size of a light (say Red) from 60X 0.85 NA objective is about 1 um

In a conventional microscope, when the spot size of the light from a 60X, 0.85 NA objective is about 1 $\mu m$ $\left(\frac{1.22\lambda}{NA}\right)$, why the area illuminated (as seen on the eyepiece) ...
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Why are the edges of the shadow so bright?

Today I noticed something while playing with my specs (having diverging lenses). Have a look at it : This is the shadow of my specs on the wall in sunlight. The region of the lens appears darker and ...
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2answers
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Why is a simple magnifying glass placed very close to the eye?

My book answer is: There is only one convex lens in simple microscope which produces virtual,erect and magnified image when object distance is less than focal length.IN this case,real rays are ...
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Physical significance of optical power

If an optical system has more than 2 thick lenses, is there a way to mathematically calculate its power (e.g. Gullstrand's equation) and if so, what is its physical significance? Thank you.
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1answer
57 views

Why can a lens be described by a fourier transform?

I am having a hard time understanding the theory behind why we can describe light passing through a lens to the focal plane as a Fourier transform and then an inverse Fourier transform. What is the ...
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1answer
311 views

How does one derive the lens maker's formula for thick lens?

The well-known equation for thin lens is: $$\frac{1}{f}=\left(\frac{n_L}{n_m}-1\right)\left(\frac{1}{R_1}-\frac{1}{R_2}\right)$$ But there's a more appropriate equation that includes the thickness of ...
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79 views

Huygens eyepiece - Cardinal Points

Can someone explain to me how I can get the cardinal points for Huygens eyepiece using the matrix method? I tried to solve it by considering two thin lenses and calculating the matrix for the system, $...
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1answer
48 views

Can anyone tell me what these two equations represent?

I've just seen these without any explanation of what the variables are or what are do they describe, I just know it should be something about convex lenses and starting fire with them. $$Q_r=C^n(-\...
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How can focal length of the human eye lens change?

Shortsightedness is due to reduced focal length and long sightedness is due to increased focal length.howcan the focal length of eye lens change overtime?
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Microscopes magnification clarification

Why is the linear magnification $m_{obj}$ defined as $\frac{-d_i^{obj}}{d_o^{obj}}$?
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1answer
21 views

How do I calculate the electric field of a dipole after passing through a collecting lens with a given NA?

How can I make the (far field) electric field of a dipole dependent on the numerical aperture of a collection lense it is passing through?
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189 views

A thick lens suffers chromatic aberration while a thin lens does not. why?

I encountered this question and has put me into thinking that, "why does not our eye lens have any aberration?". I seem to be confused by optics. I also found that 'since lenses are made up ...
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20 views

Real image by concave mirror or convex lens

My question is how exactly can we 'see' the real image ON the mirror or lens without a screen? Also if a screen is placed, for example a real image by concave mirror has formed in front of the mirror ...
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Magnetic Lens Size required to ignite a Fusion burn

What are the dimensions and/or mass of the amount of permanent magnets( NdFeB) required to magnetically focus cosmic rays such that instead of 1 muon per square centimeter per minute hitting the ...
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Lenses and uncertainty principle

I saw a video explaining the central fringe width of a single slit diffraction pattern with the uncertainty principle. It explained: as the slit size decreases, the uncertainty of the position of ...
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1answer
35 views

Efficiency of a convex lens

When the intensity of a light source is measured before and after the light passes through a convex lens, should the two intensity values theoretically be the same? In other words, can a convex lens ...
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1answer
51 views

What is the proof that we can use virtual object to know the place of formation of image in case of convex/concave lens?

What is the proof that we can use the location of virtual image in the lens formula to get the location of the image (convex/concave lens)? The following problem might make my question more clear. The ...
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3answers
26 views

Focal Length as it relates to Field of View

I understand that in physics, for a converging lens, the focal length is based on the refractive index of the lens material and its curvature. However, I started reading a bunch of photography ...
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1answer
54 views

How do fundamentally electrostatic lenses work?

I don't need any super specific answers. But I would it appreciate alot if someone could either confirm or correct my thought process. I know that for many of you this will sound super obvious but for ...

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