Questions tagged [lenses]

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction.

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2answers
27 views

Absolute refractive index and power of lens

The power of a lens is the degree by which the lens can bend light, and the absolute refractive index is also the same. What is the difference between them? Is the power of a lens an absolute ...
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Focal length of convex lens and ability of refraction [closed]

Why the convex lens of short focal length has more ability to refract the light?
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Is sign convention necessary in the following equation?

The above diagram is used to derive the following equation which is about the refraction due to the spherical surface. $$\frac{n_2}{v} - \frac{n_1}{u} = \frac {n_2-n_1}{R}$$ The above equation is ...
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Sign convention in refraction at spherical surface

While deriving the formula for refraction at spherical surfaces: $$ \frac{n_{2}}{v}-\frac{n_{1}}{u} = \frac{(n_{2}-n_{1})}{R} $$ We use the sign convention that object distance = -u Then while ...
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Why is the size of image increasing as observer moves away from lens?

I was using a convex lens and placed the object at principal axis at a distance from optical center lesser than focal length (between $F_1$ and optical center). Then I started observing the size of ...
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Derivation of Combination of thin lenses in contact: How can object (virtual) be taken at right side of a lens?

My book has the following derivation- Consider two lenses $A$ and $B$ of focal length $f_1$ and $f_2$ placed in contact with each other. Let the object be placed at a point $O$ beyond the focus of ...
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1answer
27 views

Lens theory, what sets the angle of view in photography?

Is this correct statement that - in photo equipment angle of view forms from dimensions of sensor i.e. if we draw line from top most and bottom most edge of the sensor trough center of the lens we get ...
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Changing the apparent focal distance of an object

I'm not completely confident this is the write SE site to post this on, but it seems like the most relevant one. I want to make an object (with negligible thickness) that is around one to five ...
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1answer
41 views

Is this given ray diagram for a biconvex lens correct?

Figure shows a biconvex lens of having radius of curvatures as R1 and R2 , in the ray depicted shouldnt the meeting point of the rays be at 2F and the object should be placed at -2F , where F is the ...
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1answer
89 views

Why bi-telecentric lens works with a finite focal length while it should be afocal system?

I bought a bi-telecentric lens for experiment. From all I've learned before, it accepts only axis-parelle incoming beams and exits the same parelle light, so it should be an afocal system with ...
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Hi everyone, could anyone help me understand how two cylindrical lens can be used to form a laser sheet?

If you look at the below link under 'Laser Sheet', https://www.edmundoptics.com/campaigns/cylinder-lens/ the equation is much easier for a single line generator. I am stuck at the point where I use a ...
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1answer
27 views

Incoherent imaging through two aberrations

I am doing independent research trying to isolate and solve for distortion of an incoherent target when it passes through a known distortion in the medium and then an unknown distortion in the lens ...
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85 views

Why do the eyes of a person wearing glasses not look blurry if almost everything looks blurry when I wear them?

When I wear my mother's (hyperopic) glasses, almost everything appears blurry, (the reason for which was explained in this answer). What I don't understand, is why this doesn't work backwards. ...
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1answer
37 views

Real or false image formation of a plane mirror and lens [closed]

If an object is placed in-between a plane mirror and a convex lens. Would the image that results from the reflection off the plan mirror into the lens be real. Rough diagram: Plane mirror------Object--...
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5answers
113 views

Why does magnification work?

I have read the question How do telescopes work as magnifiers? but it doesn't quite address, as far as I can tell, my question. I'm trying to wrap my head around why magnification works rather than ...
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1answer
126 views

Where is the "infinity" where image of an object kept at focus of a convex lens being formed?

Here the object is AB kept at first focal point F₁, and we see the light rays emerging parallel to each other, meeting at infinity. When the object is kept at focus of a convex lens we say that image ...
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1answer
26 views

Refractive indices of liquid crystal

Refractive indices of liquid crystal • The birefringence is critical to the optical properties of the liquid crystal and underlies many of the applications of liquid crystals. • By reorienting the ...
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How do electromagnetic lenses magnify the image?

In optical microscope both objective and eyepiece are used to magnify the sample image. Magnification is determined by laws of geometrical optics (intersection of optical beams from the same point of ...
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1answer
77 views

Deriving the thin lens formula from the lens maker formula

I've been studying refraction recently, and I faced some doubts regarding the thin lens approximation. The thin lens formula is given as : $$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$$ However, I also know ...
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30 views

Is it possible to find the magnification of multiple lenses if the object is at infinity?

I understand the ray diagram of three lenses (converging, diverging, converging not stuck together) with an object at infinity, but is it possible to calculate the magnification of the entire system? ...
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1answer
60 views

Can we see the image of inside of our eye, in front of the eye?

Yesterday, I was sitting with a really bright computer screen (brighter than usual) right in front of me (about 30 cm) and it was like a cubicle (most of the light was blocked from all 3 sides — front,...
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3answers
70 views

Convex lens in our Eyes

I just learned that our eyes are made up of bi-convex lens, and I know that convex lens are also called converging lens since they converge to form real images that can be caught on a screen. But why ...
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1answer
41 views

Why objects dont appear closer and smaller to a myopic person and far and larger to hypermetropic person after wearing spects?

I am a myopic person, and wear a concave lens. It is taught to us that lens I wear help to form image on my far point and thus help me to see far object. 1.But we have also learn that concave lens ...
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1answer
36 views

Optimising the choice of lens for collecting scattered light

I want to figure out the “best” lens for collecting light that is being scattered in air. For simplicity, lets say that the scattered light in the volume of interest is homogenous – i.e. the intensity ...
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1answer
27 views

Can we use meniscus lens for objective in a telescope?

I am making a telescope, but I had meniscus lens of power +1 (so focal length 1 Metre). I brought it in a optic store since I cannot find the lens of my need in any shop in my city. When I put it in ...
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1answer
48 views

"Aperture size is much smaller than focal length of the lens"

My theory is limited in this regard so I had a little doubt. I often see it mentioned in the problems that "assume aperture size of lens much smaller than its focal length" what does this ...
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1answer
64 views

A lens with a high permeability

In real life materials with high $\mu$ values are not realistic, so lenses are made with high $\epsilon$ materials. But what would be the impact of achieving the same refractive index by increasing $\...
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1answer
30 views

What type of lenses or a combination of optics do I need to reduce a flashlight beam size?

Optics is not my best subject. I know the basics of how light behaves as it go through a lens. I tried to understand further but got more confused as I get deeper into this subject. My goal is to make ...
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1answer
54 views

Why do we consider the optical path length constant in a Cartesian Oval

I admit that this was from a homework question, but I'm having huge trouble wrapping my head around why the optical path length needs to be the same for a Lens that focuses every single ray emanating ...
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1answer
39 views

Question regarding Newton's rings

In the Newton's Ring Experiment why is the central fringe a light fringe? Why does constructive interference happen at the center? Does it have anything to do with the sense of thickness between point ...
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51 views

What materials can bend or reflect gamma rays?

I have heard that gold can be used as a lens for gamma rays, but what exactly could reflect them? Having this technology could make something like a Dyson sphere much more efficient, I believe.
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23 views

Convex and Concave lenses

Why does concave lens diverge light even though it seems pointing towards 2F and why does convex lens converge light even though it is bulged out? (The lenses are same shape on both sides here)
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1answer
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Where is the optical centre of a Concavo convex lens?

I have been taught that the Optical Centre of a lens is the point at the principal axis of a thin lens through which Ray of light passes undeviated. I was under the impression that it always passes ...
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1answer
43 views

Focussing lens placed after double slit experiment

How would the expression for the intensity distribution produced by a double slit on a screen change if a focussing lens of focal length $f$ were placed a distance $f$ in front of the screen? Note: ...
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1answer
54 views

Angular aperture of diverging beam after passing through a diverging lens

Consider an optical set-up as shown in the plot below: A light source, e.g. a laser diode, of diameter $d$ ($\approx$ 1 mm, but numbers are unimportant) is emitting a divergent beam having a half ...
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2answers
78 views

Does an aspheric lens require that the incident light be collimated in order to focus it?

Aspheric lenses are able to either collimate or focus light, depending on the side of the lens the light is incident. In diagrams that show the aspheric lens focusing light, the incident light rays ...
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Why doesn't a light ray bend again when emerging from a lens?

This image is a representation for light passing through a convex lens. It shows light entering from air to glass. When the light enters the glass we can see that it bends towards the normal. Now when ...
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1answer
34 views

Determine lens system for known magnification and available space

I'm trying to create a system of two lenses with a set magnification in a limited space for the setup, i.e. the distance from the object to the first lens $g_1$ has a minimum ($152\,$cm) and the whole ...
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Focal length of Abbe condenser

I am looking for the focal length of a Abbe condenser, i.e. Olympus U-AC2. I cannot find this number at microscope specification sheets nor anywhere else on the internet. Is there a similar way of ...
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What exactly an angular information which is gained from a ray transfer matrix means?

$$ \begin{pmatrix} x_{\text{i}} \\ v_{\text{i}} \\ \end{pmatrix}=\begin{pmatrix} 1-\frac{ d_{\text{i}} }{ f } & d_{\text{o}} + d_{\text{i}} -\frac{ d_{\text{o}} d_{\text{i}} }{ f } \\...
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1answer
143 views

Since a collimated beam is always in focus, can't I simply just emit a collimated beam over the varying distances as the target object moves?

I am designing an interferometer for an experiment. The setup consists of (1) the laser source, (2) the interferometer itself (consisting of optical components and photodetector(s)), and (3) the ...
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0answers
85 views

How does the quality of the reflected light compare to the emitted light? And how do I manage this (reflected) light quality well?

I am designing an interferometer for an experiment. The setup consists of (1) the laser source, (2) the interferometer itself (consisting of optical components and photodetector(s)), and (3) the ...
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1answer
31 views

In the optical bench experiment of two pins( the object and image pin) kept on either side of convex lens. Why the real image appears on the lens?

Since real images can only be seen on screen why are we able to see it on the lens. Will it not be called virtual?
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1answer
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In case of convex lens we find real images on it as up side down although real images can only be seen on screen. How do we see them on the lens?

In case of convex lens we find real images on it as up side down although real images can only be seen on screen. How do we see them on the lens?
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The equation governing lens systems [duplicate]

In some sites, I find the lens equation to be (eg: pg-6 of this pdf): $$ \frac{1}{u} + \frac{1}{v} = \frac{1}{f}$$ And other sites I find it to be (eg: 5:58 of this video), $$ \frac{1}{v} - \frac{1}{u}...
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How does beam shape (elliptical vs circular/Gaussian) affect interferometry?

I want to understand the importance of beam quality to interferometer systems. This article says the following: A very high (close to diffraction-limited) beam quality, associated with a high spatial ...
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1answer
38 views

How does the effective focal length work for aspheric lenses? How should I select an aspheric lens?

I am currently looking at aspheric lenses on Thorlabs. I want to use them as a collimation optic for my interferometry experiment. Note that the lenses have a listed EFL (effective focal length). But ...
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1answer
44 views

Working of liquid lens

we were recently introduced to the liquid lens in school, but i havent quite understood the working of it. I realize that the curvature of the lens is changed by some process, but i dont exactly know ...
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1answer
17 views

Interferometry: effect of aspheric lens on self-mixing effect

I want to perform self-mixing interferometry experiments using a laser diode, as was done here. I'm going to use a low-power laser diode. However, I want to improve the performance of the device, ...
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1answer
29 views

Is it possible to build a lens system that allows you to capture an orthographic projection of the real world? [closed]

I am a bit of a computer graphics geek and I find it fascinating how difficult it is to wrap ones mind around what an orthographic projection looks like as the world rotates. I know nothing about the ...

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