Questions tagged [lenses]

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1answer
17 views

If final image of object is forming at viewer's eye, where will viewer see that object?

If an object is kept at centre of curvature of convex lens and a viewer is present at centre of curvature of other side then where will he see that object? I think he will see the object at it's ...
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1answer
46 views

Why do parallel light beams converge at the focal point of a curved mirror?

Can someone prove that all parallel lights beams reflect back and meet at point the point $F$? Any help would be appreciated.
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1answer
23 views

Can all aberrations be fully removed by a lens system in theory?

I recently came across an interesting argument (in Mack's "Fundamental Principles of Optical Lithography", beginning of Chapter 3): By adding more and more lenses to an imaging system, more and more ...
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0answers
10 views

Why is the reflection of CFL bulb a green spot on my glasses

Why is that if i try to see the reflection of a CFL bulb (the bulb is on) using my glasses i see it as 2 green spots instead of a white light. plus this happens on the outerside of the lenses...not ...
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24 views

Change of a lens' focal point with wavelength. Refractive index wavelength independent

I was using a Comsol example for the focusing lens: https://www.comsol.com/model/focusing-lens-57621 I made no changes to the model. The focal length of the lens is set to be 1000 um. Initially, I ...
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0answers
40 views

Infinity Corrected Microscope vs. $4f$ imaging system

This questions concerns three types of microscope systems and the differences between them. Let me lay out my understanding of these three types of systems. I am imagining imaging with a camera so ...
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0answers
20 views

Designing of a Lens-Optical System

I need the following guidance & help related to designing of a specific type of Optical System Lens Design. Which tool is freely (open source) can be used? is there any possibility of doing a ...
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0answers
26 views

Real image in optics

A real image can be seen on a screen, right. But how we see a real image without a screen, when we have to find out the focal length of convex mirror with the help of a covex lens during class ...
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1answer
20 views

What is the difference between longitudinal chromatic aberration and spherochromatism?

In lens design textbooks, a distinction is often made between longitudinal chromatic aberration and spherochromatism. (See for instance Kingslake's lens design book.) What is simple way to understand ...
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0answers
54 views

Gravitational lensing in the form of optical equation $\frac{1}{p} + \frac{1}{q} = \frac{1}{f}$? [duplicate]

Gravitational lensing and light deviation is a well known subject in General Relativity. I'm wondering if the null geodesics equation could be recast into the classical lenses equation: \begin{...
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2answers
16k views

Difference between convexo-concave and concavo-convex lenses?

What is the difference between concavo-convex and convexo-concave lenses? We dont say convexo-plane for plano-convex. Does that mean concavo-convex and convexo-concave are essentially the same?
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1answer
17 views

Calculated focus of an asymmetric bi-convex lens

So I've been working on modeling an optical system using ray tracing. I've finally gotten to the point where I am testing things however I've come across something I'm not entirely sure of. I'm ...
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1answer
184 views

Numerical Aperture

I have some questions regarding numerical aperture. Let's say there is a glass lens and a light source to the left of the lens. You can then draw a cone to the lens. Let's say the light rays get ...
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3answers
61 views

Lens with focal length 0

I have been wondering about a limiting case of the focal length. Specifically, a lens with a focal length of $0$. Could that exist in real life, and what would be its meaning? Also, what does it mean ...
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2answers
435 views

Why don't we use sign convention during the derivation of a lens maker formula?

Please have a look at the Lens makers formula. In any derivation of Geometrical optics, we use the sign convention twice: once while deriving it and next while using it for general cases. But in the ...
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16 views

Gradient Constant of a Gradient Index (GRIN) Lens

I came across this page https://spie.org/publications/tt48_55_gradient_index_lens and was wondering how one would go about calculating the gradient constant, k in this example.
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1answer
24 views

Regarding the demonstration of Poisson's Spot

This video is one by Veritasium on Poisson's Spot. https://youtu.be/y9c8oZ49pFc In the later half of the video where he does the experiment by using a laser, why does the laser beam have to pass ...
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2answers
22 views

Final Image Position with Multiple Lenses

I am confused on how to calculate the final image position after the two lenses. I understand that the image position of the first lens can be treated as the object position of the second lens, but in ...
4
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3answers
156 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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0answers
12 views

Why does the images of slit slip down in bottom as we move the lens?

Why does the images of slit slip down in bottom as we move the convex lens in the experiment of "determination of wavelength of sodium light by fresnel biprism experiment". We made the system coaxial ...
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0answers
21 views

Telecentric lens references, working distance formula

I would like to learn about telecentric lenses for use in an experiment. So far, I have found scant resources (mostly optical companies) and I understand the basic principal of a simple telecentric ...
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1answer
5k views

How do you calculate the angular magnification?

This is one of my practice problems for my upcoming exam. I'm supposed to find the position of the image and the angular magnification. A small insect is placed 6.35 cm from a 7.00 cm -focal-length ...
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2answers
90 views

Concave magnifier lens Two questions in one [closed]

Consider a support made from a wide (1m), short (30cm) (approximate sizes just for reference), rigid, empty, open ended cylinder. Cover the ends with a perfectly flexible transparent sheet. Suck the ...
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0answers
16 views

Image position in general lenses

Looking for a general equation that relates the position of objects and images. This equation is valid for all systems: thick lenses, aspheric, doublets, triplets in any size? 1/s1 + 1/s2 = 1/efl
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4answers
163 views

determining focal length of converging lens

the focal length is the distance between the center of the convex lens and the focal point. in the image illustrated above, we obtain focused image at the (position of image, inverted yellow arrow) ...
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0answers
15 views

Thin lens thickness design

Is there a rule for the thin lens thickness so that it follows the para-axial approximation either with respect to the wavelength or the radius of the lens?
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2answers
378 views

Light focusing on long distances

If I have a green laser (500 nm wavelength) with initial beam diameter 3 mm, with proper lenses I can easily focus it to 1 mm or 0.5 mm for small distances like 10 cm. My question is can I focus it ...
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0answers
27 views

How I can add lenses stacked on front of iphone camera to increase magnifying power?

How we can stack different lenses to increase magnifiying power of a smartphone camera? Is there any way to test if stacked lenses will focus light on image sensor of smartphone exactly right before ...
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0answers
14 views

Question regarding demonstration of Poisson's spot [duplicate]

https://youtu.be/y9c8oZ49pFc At around 5 minutes into the video, to show Poisson's spot, the laser beam is made to go through a diverging lens. Is it necessary to use a diverging and why?
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0answers
23 views

Question about transmission of paraboloidal light waves in bi-convex lens

The question is as follows: Show that a paraboloidal wave centered at $z_1$ is converted by a lens of focal length $f$ into a paraboloidal wave centered about $z_2$, where $\frac1{z1} + \frac1{z2} ...
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1answer
932 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
35 views

Is there a way to add lenses together to shorten their focal length?

I need to know if there is a way to put lenses in front of each other to make their focal length shorter. I tried putting them directly in front of on another, but I wasn't sure if there was a better ...
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0answers
9 views

Magnification of a compound micrscope

What is the formula to find the magnification of a compund microscope if the focal lengths of the two lenses and the distance between them are given.
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1answer
45 views

Lens Formula for thick lens

My textbook states that for thin lens formula of lens is i.e $\frac{1}{v}$ - $ \frac{1}{u}$= $ \frac{1}{f}$ and for thick lens $ \frac{1}{v-t}$ $ -\frac{1}{u+t}$ $= \frac{1}{f}$ While the ...
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1answer
79 views

(7) Will a nearsighted person who wears corrective lenses in her glasses be able to see clearly underwater when wearing those glasses? [closed]

Will a nearsighted person who wears corrective lenses in her glasses be able to see clearly underwater when wearing those glasses?
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3answers
2k views

Do eye-glasses decrease the Depth of focus?

I was reading up about Depth of Focus and wondered if glasses affect depth of focus. If yes, is it noticeable to the user?
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2answers
36 views

What type of lens is used to collimate light?

I am interested in collimating infrared LEDs, but I don't know what type of lens to use (eg, concave or convex). Can someone tell me what type of lens to use? I am trying to collimate a regular IR LED ...
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1answer
205 views

Does a lens with a given numerical aperture (NA) increase etendue, even if it follows a source (e.g. fiber) with lower NA?

It is well known that the etendue of an optical system cannot be decreased - i.e. the brightness of a source cannot simply be increased by using lenses to try and focus something more tightly. ...
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0answers
17 views

Polishing Spherical Refracting surface vs Lens

My text book states that When we polish a spherical refracting surface (sphere) it doesn't behave as spherical surface and mirror .It still behaves as spherical surface. The polished side is just ...
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1answer
180 views

Sign Conventions in Mirror/Lens formula

All textbooks I've come across have the same way of proving the mirror formula. Everything makes sense, except the fact that they apply the sign convention once to obtain the mirror/lens formula, but ...
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1answer
24 views

Image formation and focus

It is known that an image is in focus (and it results sharp and clear) only at the focus, in which all rays intersect themselves. Why do we see sharp images only at the point in which the rays emitted ...
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0answers
9 views

Lens simulator with geometrical optics [duplicate]

I'm looking for a lens simulator to see rays from geometrical optics, possibly easy to use. For now I'm playing with OpticalRayTracer that works perfectly for a preliminary simulation. I would like a ...
2
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1answer
31 views

Where does energy come from when a laser bean exits lens at c?

Take a laser. Fire it at a lens. Prior to arrival at the lens the lasers pulsed beam’s speed is c. Traversing the lens it’s speed is less than c. Exiting the lens (and back to the vacuum) it’s speed ...
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1answer
46 views

Lens design with few constraints

I'm not an expert in lens design. I need to build a lens having fixed the focal point $f$, the lens diameter $D$, the maximum thickness $d$, the refractive index $n$ and the half-angle $\theta$ ...
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2answers
55 views

Which side is convex in my plano convex lens?

So, I am building an optical system and have got a Thorlabs plano-convex lens (part # LA1172-C) with a 400mm focal length. This makes the convex side of the lens so flat that it is difficult for me to ...
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0answers
24 views

How far will the imaging be? And is it possible to make it farther?

So currently I'm trying to make a smart glasses, where you have a projector that projects an image onto transparent flat glass, and some of the light will reflect into your eyes (something like the ...
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0answers
36 views

Raytracing on convex spherical surface, where n1>n2

I'm reading my textbook and I'm trying to figure the ray tracing of a single point of this one case that the book doesn't cover. My question is, what does the ray tracing look like when we have a ...
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2answers
50 views

How do lens capture reflections clearly?

In an optical system which uses lenses (cameras, our eye) multiple rays from the same point are conveyed in a single point on the retina / image sensor. This is typically shown as in the image below. ...
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1answer
28 views

Focal Length, Wavelength Relationship

I have a cylindrical lens with a design wavelength of 587.6nm. The radius (S2) of the lens is 2mm, and the radius of the opposite face (S1), i assume is 0mm. The focal length is given as 3.91mm and ...
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1answer
32 views

Telecentric lens system with gaussian optics

I often use bi-telecentric lenses at work, which means both object-side and image-side chief rays are parallel. However, as I don't really have an optics background, I'm a bit baffled at how this ...