Questions tagged [lenses]

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61 views

If you have 2 lenses, is it better to place the stronger lens first or the other way around?

I need to focus a laser at a certain distance. But everytime I perform the experiment, the distance between the laser and the surface will be slightly different. Therefore I will fix the lens with the ...
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0answers
14 views

Concave Lens Magnficiation

Is there some formula to calculate how large an image of a light source will appear on a screen based on the lenses distance from the image and the lenses distsance from the screen? For example, if ...
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3answers
109 views

Why do lens (convex) not introduce any path difference to light incident on it?

My understanding is that the top rays spend less time inside the lens where the speed of light is slow and the middle rays spend more time inside the lens so the time is kind of compensated . But I'm ...
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3answers
180 views

Identifying real and virtual images (convex lens experiment)

I m really confused between virtual and real images. While doing a convex lens experiment using optical bench (I have attached an image), when I look through the lens I see an inverted image. As this ...
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1answer
63 views

Can telescope have dual purpose? [duplicate]

Astronomical telescope has a small eye piece and a large objective lens. Whereas a compound microscope has a large eye piece and small objective lens. Therefore can we use astronomical telescope as ...
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2answers
34 views

Significance of image position

Consider the case of image formation in the convex lens when the object is placed between f and 2f its image will be formed beyond 2f on the other side. And the image position is said to be the point ...
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0answers
157 views

Fourier transforming properties of a converging lens

Following Goodman's Introduction to fourier Optics argument I understand that a converging lens will introduce the following difference in optical path (see pag.158, 4th edition) $$r^2/2f$$ where $r$...
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33 views

Convex lens image formation

I've been trying to get the image of an object (2-D image) after reflection by a lens. I've been searching for a solution, but I always get the image formed from a 1-D arrow. For example, this answer ...
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1answer
89 views

Prescription glasses curved design

Typically, prescription glasses are built with a pair of lenses oriented in a straight line with very little deviation from 180° angle (Figure 1(a)). However, protective or sport goggles (no dioptres) ...
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1answer
41 views

What is the name of this lens design that uses concentric dark and transparent rings?

I remember from my optics class years ago that one can make an optical lens out of a set of concentric rings, alternatively transparent and dark. By choosing the diameter and width of said rings, the ...
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1answer
19 views

What kind of lens would eliminate distortion through a cylinder wall?

Suppose you are trying to look at an object inside of an acrylic cylinder. What kind of lens could you use on the outside to eliminate the distortion caused by the wall? The image can be inverted.
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2answers
64 views

How can I focus an optical device at infinity, inside a room with limited space?

I have a custom coupled camera/spectrograph imaging system that I need to focus at infinity for a microscope setup. I can't move the device outside, where I would be able to use some distant object to ...
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2answers
46 views

Light hitting a GRIN (Gradient-index) lens at the optical angle

In the image below, rays of light are hitting the GRIN (Gradient-index) lens at the optical angle and then converge towards the optical axis. Why do they do this? The refractive index is only a ...
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0answers
81 views

What are laser achromats?

I came across "we used Nd:YAG laser achromats" in a paper, and I was wondering what exactly is the purpose of achromats here. The paper in question is "Dynamics of laser-induced cavitation bubbles ...
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1answer
84 views

Sign convention in optic problems

Note: The convention used in our physics textbook and the mentioned question is Cartesion Convention Today in our physics test, we were given the following question:- A mirror has focal length 20 cm ...
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1answer
414 views

Why don't we see inverted image while wearing spectacles? [closed]

We know that the lens in our eyes forms an inverted image on retina and brain reverses it to give the correct image. But when one wears specs the image would get reversed twice so we should see things ...
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0answers
39 views

working to understand virtual images

I'm starting to understand how to use lenses a bit more, but I'm still pretty lost. I'm building a project that's extremely similar to this one with the implementation. I think my biggest challenge ...
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2answers
86 views

image formation by lenses

Why is the image formed by an object as described in the picture can be derived only from these three ray of lights?Every point on the object has multiple ray of lights going in every direction, how ...
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0answers
26 views

Is the focal length of a lens for light in one direction necessarily the same as for light in the opposite direction?

Suppose there is air at one side of a lens, and water at the other, such as in the human eye. Is the focal length for light in the direction from air to water then different from that for light in the ...
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4answers
2k views

What are the differences between Convex Lens and Convex Mirrors?

Sometimes I heard my teacher said convex 'lens' but other time I heard he said convex 'mirror'. The main problem I am currently facing right now is using the right terminology. In other words, what is ...
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1answer
120 views

Is image seen in optical bench experiment using two pin and convex lens real or virtual? [duplicate]

Is the inverted image formed in optical bench experiment using two pins and convex lens real or virtual ? how am i able to see it without screen if it is real ? we clearly see an inverted image of ...
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0answers
653 views

Why do my glasses make the ground look tilted?

I just started wearing glasses to correct my myopia today. I have -0.25 spherical and cylindrical power in my right eye and -0.5 spherical and -0.25 cylindrical in the left eye. Everytime I look at ...
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2answers
61 views

Is this possible to focus common light (not laser) to a small point in the wall and control it with mirrors?

I want to make something like a laser projector for an experiment but with common light. My question is: is this possible to focus a small point of common light to the wall and control it with ...
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1answer
268 views

What will happen if the refractive index of lens is less than unity? [duplicate]

Generally the refractive index of any lens is greater than air. My question is what will happen if the refractive index of lens is less than unity?
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2answers
935 views

Focal length of magnifying glass

Why a magnifying glass has a short focal length? According to its work the object must be between the focus and the optical centre, a large focal length will favour it, then why is it so?
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2answers
356 views

Does a biconvex lens have a shorter focal length than a plano-convex lens?

Is there a ray-tracing diagram somewhere that shows precisely the difference between a Biconvex and Plano-convex lens?
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1answer
44 views

The focal length of spherical mirrors

How are the focal length, the object distance and the image distance related?
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2answers
1k views

Image formed via a converging lens when the object is placed at focal point

In the case where the object is placed at focal point F of a converging lens, the rays of light (the one passing through O and the one sent parallel to the principal axis never meet) so I am assuming ...
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3answers
201 views

Can a lens be used at radio frequency?

Lenses and Antennas are two means of manipulating EM waves. While antennas are predominantly used at RF / Microwave frequencies, Lenses are used for optical/IR regions of the spectrum. I understand ...
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1answer
49 views

The electric field in the focal length of a strongly focused lens

I have a Laguerre Gaussian beam and I want to focus it by using a strongly focusing lens. But my question is that I don't know what will happen to the electric field structure in the focal length ...
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1answer
32 views

Raise index of refraction of spherical lens

What happens to focal length and aperture of a spherical lens if you raise the index of refraction of the glass?
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2answers
463 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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4answers
86 views

What does the intensity profile of a set of parallel rays look like after travelling through a convex lens?

I have had a discussion at my university about the following question. Imagine a 'perfect' convex lens and a set of parallel rays, falling onto that lens. The set of incoming rays has a flat intensity ...
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1answer
492 views

What happens if we cut a convex lens horizontally?

Does the focal length change? Or does it remain constant and only the brightness of the image is reduced?
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1answer
58 views

Refractive screen for myopia [closed]

Is it possible to create a screen for a computer monitor to allow a Myopic person to see the screen without glasses?
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1answer
176 views

Looking through a glass hemisphere [closed]

I've found the following question on IsaacPhysics.org . I've been working on it for a couple of hours but I cannot figure it out. A looking glass is used to read an ancient scroll. This lens has a ...
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1answer
221 views

Principal focus question

On my notes İ have written that the definition of principle focus is : the point on the principal axes where rays appear to diverge or rays actually converge. However İ was looking at this diagram of ...
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2answers
102 views

Question about lenses in the human eye

To see near objects,the ciliary muscles contract and the suspensary ligaments loosen,making the lense thicker. İ don't understand how that helps us to see distant objects . To see distant objects ...
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2answers
71 views

Does anti-blue coating work less effective on high power lens?

I purchased a spectacle from an online website with anti-blue coating. The features of this product is mention here. Once I receive it, I started using the product without testing the anti-blue ...
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3answers
143 views

How lens works in eyeglasses for distance and near vision?

Consider someone who wears a Contact Lens that is -10.00 diopters in power (very powerful) for distance correction, but needs +2.00 diopters ADD reading glasses "over-the-top" of the contacts to be ...
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2answers
71 views

Imaging resolution with laser

The transverse optical resolution of a lens, as determined by its point spread function, can be approximated as $w$ ~ λ/(2$NA$), where $NA$ is the numerical aperture and λ is the wavelength of the ...
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2answers
99 views

Magnification of Objective Lens

Where should we place an object to get 10x magnification with a 10x objective lens? we know that objective lens can be modeled with a simple positive lens so magnification should be dependent on the ...
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0answers
51 views

Effects of lenses

I have three convex lenses that I'm arranging so as to function as a crude magnification device. My question is about the image that I see. It seems that no matter how I arrange them, with respect to ...
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2answers
330 views

Why does shorter focal length result in greater beam divergence?

So I got 2 converging Fresnel lenses, one with 50 mm focal length and other 70 mm. My experiment looks like this: When trying to focus and SMD LED emitter into a narrow beam (sticking to lenses ...
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1answer
534 views

Newton's ring conceptual doubt

Newton’s rings are formed as a result of interference between light waves reflected from the upper and lower surfaces of the air film developed between the convex surface of the plano-convex lens and ...
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2answers
189 views

How do we prove that parallel light rays (which are not parallel of principal axis) meet at focal plane?

Parallel rays coming from infinity are said to meet at focal plane.I was looking for the proof of that phenomena
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3answers
84 views

Why do we need telescopes/ binoculars/ etc? [closed]

Why do we need to use magnifying objects to see things that are far from us? Why isn't the light coming from those objects enough for us to see without special aid? Is it because light loses energy on ...
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1answer
101 views

What refractive index should be used while calculating the focal length of lens using lensmaker's formula?

Suppose a lens is half dipped in liquid. Then should the refractive index of liquid with respect to air should be taken. Or should refractive index of glass wih respect to liquid be taken. Or perhaps ...
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1answer
194 views

Calculating pupil magnification

Is it possible to calculate pupil magnification, given that these lens parameters are known: focal length f-number at infinity focus positions of front and back principal points position of the ...
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1answer
119 views

Front/rear effective diameter on a camera lens

I'm in the process of trying to understand lenses a bit better so I decided to take a look at the specs of an actual lens I have access to: Kowa LM25HC (datasheet). Can someone explain the meaning of ...