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Questions tagged [lenses]

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What is the definition of a Projection? [on hold]

This may be a stupid question. But here it is... Can the scenarios below be reffered to as projections? 1) A projector projects an image onto a white screen. 2) A LCD display forms an image on a ...
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10 views

Question about adjusting focus on augmented reality

I am working on a project and I am trying to build augmented reality glasses. I have a question about focusing the projection from screen and the real object on the far distance at the same time. How ...
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21 views

Formulas with complete sign conventions for spherical mirrors and thin lenses

I'm looking for two things: Something like the third equation in the chosen answer in the link, but for spherical mirrors, and Something that covers conventions for the radii of curvature and focal ...
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1answer
22 views

Why do we need an objective lens in a scanning electron microscope?

I've been studying scanning electron microscopes quite a bit but can't seem to get my head around why we need objective lenses. On paper I don't see a reason, if we would want to focus the electron ...
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1answer
39 views

What kind of lens does the opposite of magnifying?

I know nothing about physics, so I figured I would ask here. I am doing an art project, for which I need an lens that has the opposite effect of a magnifying lens, that is, to make whatever you're ...
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1answer
42 views

In non-technical terms, how does the scanning electron microscope function?

I've watched a few videos like this one and know the basic structure. We have an e-source, an anode which pulls electrons out, then a condenser which starts to focus all beams, scanning coils and ...
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1answer
34 views

Why do I need a longer focal length to take a picture far away?

Can someone tell me why I need to use a lens with a longer focal length when aiming to take pictures of distant objects?
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3answers
92 views

How do we see virtual images?

Here in the diagram rays coming from B' point falls on two different places on retina of eye.So we should see B' at two different places. But it doesn't happen like that in reality. Is my logic wrong? ...
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1answer
26 views

The change of focal distance as a result of adding a substance

I have a given focal distance between lens and an image sensor (in air). Now I add a protective glass with a known refractive index and width between the lens and the sensor. How can I calculate the ...
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0answers
33 views

How to shift light to a longer wavelength / lower frequency energy level so that it becomes a different “color”?

I need to shift light from a certain wavelength/frequency to another, lower, level. For example, green light down to yellow or orange. I want to reduce the energy level of the transmitted light, for ...
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39 views

Experimental Calculating Optical Lens for Temperature IR Sensor. (heat emitting 20x20cm object in a distance from 13cm)

I need to calculate online heating temperature of thermoplastic by the MLX90614 IR Sensor shown blow: used in one Vacuum former device. As you can see i need to calculate the thermal plastic ...
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2answers
103 views

Question about zooming out with optical lens

I need some help. I am working on a project and I am wondering if it is possible to make an object to look 100 times far away than it is actually using lens (or more than one lens). The lens (or ...
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4answers
190 views

What happens when one side of a convex lens is made fully reflecting?

Assume that I have got a bowl half-filled with mercury. In this bowl, I place a convex lens which make one side of the lens fully reflecting. What will happen to the lens, will it behave like a ...
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1answer
39 views

Image formation of object on itself by a system of a lens and a mirror

Suppose there is a lens and a mirror. An object is placed in front of this system (nearer to the lens). If the final image of object (refraction, reflection and again refraction) is formed on the ...
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1answer
83 views

What would a lens-less world look like to us? [closed]

The images we perceive through our eyes are formed by focusing the incoming light with the eye's cornea and lens. The information is "captured" by the retina and then transmitted to our brains through ...
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0answers
40 views

Problem related to combination of lens & equivalent focal length and lens maker's formula [closed]

in between two equiconvex lens( made of glass) of focal length of 20cm there is a layer of water which also acts as a convex lens.The whole figure is surrounded by air. Find out it's equivalent focal ...
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1answer
23 views

Overall power/focal length of an eye and corrective lens system

Hey. I got this question wrong and I don’t get the explanation. I know that to fix myopia you need a concave lens to diverge the light rays so that the eye lens converges them further back on the ...
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1answer
49 views

How do I explain the below phenomenon I am seeing along the edges of my eyeglass lenses?

I am near-sighted. Here is the phenomenon: I stand in front of a light source that is situated on the ceiling so that it reflects off my eyeglass lenses and appears circular. It is a white light ...
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1answer
29 views

Formula for blurring out a grid of holes

Place a camera lens with focal length f_l mm and camera sensor size w mm and h mm behind an ...
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0answers
25 views

Thin Lens Approximation [duplicate]

Why is ray travelling through pole passes undeviated?( not changing any direction) ( this was asked in kvpy interview)
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1answer
41 views

If I have an IR source, would glass lenses work in focusing them at a point?

So I'm using near-infrared light of the wavelength of order 700-800 nm. I need it focused at one point. I was wondering if using glass lenses would do the job or not?
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1answer
22 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
73 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
32 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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18 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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0answers
31 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
109 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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22 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
28 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
43 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
55 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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1answer
34 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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3answers
104 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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23 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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2answers
28 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 ...
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0answers
14 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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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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2answers
92 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
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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0answers
31 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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1answer
26 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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0answers
45 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
37 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
12 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
282 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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2answers
62 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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0answers
21 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
190 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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1answer
25 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 ...