# 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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### RAY OPTICS ( LENS AND SPLITTING OF LIGHT )

I came across a question in my book where I was asked if white light splits when it passes through biconvex lens. Could someone help me with this. I am a bit confused. I feel it won't split.
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### How to choose the right lens for projecting a certain area to a fiber optic

I am looking for a lens to magnify a certain area so that it can be captured by a fiber optic. Specifically, I want the fiber optic to capture a certain object, which requires it to be at a distance ...
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### Can we apply lens makers formula when medium on either side of the lens is different?

Lens maker's formula, which is $\frac{1}{f} = ({n_{liquid}{-1}}) [(\frac{1}{R}) - (\frac{-1}{R})]$. Can one apply lens makers formula when medium is different on both sides? If NO, why? Should we use ...
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### What is the significance of back focal length in a lens?

I work with C-mount cameras a lot and I've noticed that the lens' manufacturers often list back focal length (BFL) among optical specifications. (That's the distance between the lens' last optical ...
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### Can we apply lens makers formula when medium on both side of lens is different? [closed]

A symmetric biconvex lens of radius of curvature $R$ and made of glass of refractive index $1.5$, is place on a layer of liquid placed on top of a plane mirror as shown in the figure. An optical ...
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### What lenses are generally used to focus a beam of light into a horizontal line?

I am trying to find out more about the inner workings of a laser scanner I'm using to map objects. In this case the technical details are quite hard to come by. The laser scanner generates a beam of ...
41 views

### Can we tell on which side of a lens an image appears?

Suppose I look through a single, thin, converging lens at an object on the opposite side. Depending on where the object is placed, the lens will either produce a real image on the side of the lens ...
1 vote
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### What kind of lense do you need to use to get a picture of the sun that looks like this?

This is a picture of the sun from the moon. When I look at the sun with my eyes, I see something like this: But the above picture is perfectly round, which makes me think it has to do with the shape ...
50 views

### Do prescribed glasses transmit light? [closed]

If prescribed glasses can transmit light, what percentage of light can it transmit.
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### Geometric optics explanation of lateral (transverse) chromatic aberration

The majority of pictures explaining lateral(transverse) chromatic aberration look like this Here the focal point for red light is shifted closer to the optical axis and the focal point for blue light ...
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### Path of ray of light through a stack of lenses [closed]

The given question is as follows there are a large number of thin lenses all with focal length f separated by a distance l with their optical axes coinciding a ray starts at a height h parallel to the ...
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### How does the combination of lens create a sharper image?

There's a line in a book which states that the combination of lens helps create a sharper image, but I don't understand how. Does more magnification mean sharper image?
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### Lens and plane mirror [closed]

What is the proof for focal length of this combination being equal to half of convex lens? I tried with equivalent focal length formula but then feq = f itself as the focal length of plane mirror is ...
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### How to calculate the minimum distance where a USB cam provides sharp footage?

Can one calculate the minimum distance for a USB cam at which images appear sharp only from the focal length. Let's take this webcam from elpcctv as example. The focal length is 2.8mm and the sensor ...
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### Figuring out Lens Magnification to be Able to Focus on Screen in Front of Face

Being very interested in how VR/AR headsets work, I want to figure out the physics of looking at a screen right in front of one's face, figuring out the limits and parameters to what one could ...
1 vote
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### Why is Bessel's method more accurate than thin lens equation when determining focal length?

I have just completed a physics practical where we had to measure the focal lengths of various lenses using the thin lens equation and then Bessel's method. The task then asked for an explanation of ...
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### Why do eyeglasses use meniscus lenses?

Any eyeglasses prescription could be filled exactly with "symmetrically-shaped" lenses. E.g., a far-sighted person could use a symmetric biconvex lens (i.e., the normal "magnifying ...
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### Why aren't negative diopter glasses invisible?

If the diopters of a set of glasses determine the thickness, and higher diopters determine a thicker glass, why aren't negative diopter glass lens invisible? 1 vote
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### Heating things with a lens. Theoretical limit vs. energy conservation

Recently I've heard that you can't heat up stuff beyond sun's surface temperature using sun+lens combination. It is because you can't transport heat from colder object to a hotter object. Of course, ...
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### Calculating lens size for head mounted display

I am trying to make a single-eye head mounted display in order to use with Drone - to see video from a drone with one eye and see drone with another one. I have a 2.9" display (size of image is ...
44 views

### How can we show that a lens is a low pass filter?

I understand from the derivation in Goodman Chapter 6 that a lens Fourier transforms light from the front focal plane onto the back focal plane, ignoring aperture effects. I've also read that a lens ...
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### Does this work to reduce eyes strain? Enlarge the PC monitor with a lens

I have an idea to reduce eyes strain, but don't know if it works. I work by looking at PC monitor all day long and I believe my myopia condition is getting worse and eyes strain occurs are due to ...
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### Can a "movie" Holographic Optical Element be used to track the sun for solar collection without any motor needed?

I remember seeing a holographic movie once (at the Franklin Institute in Philly, PA), where the picture changed according to the users position (or perspective). Also, I remember a statement that a ...
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### How one explain the formation of interference in the intersection of rays from images ? Is wave nature is getting considered?

Setup below shows a (modified billet split lens setup) where two point light sources which emits wavelengths of same value and also they are in phase [Assume] . Now consider the rays which are getting ...
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### Physics behind the billet split lens method to form the interference pattern and how to accurately do it?

We know that Billet split lens is used to form interference pattern on a screen , my question is consider setup like of cut convex lens being placed symmetrically apart from each other by 2z distance ...
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### Facing difficulty in geometric optic: What is the scientific use of the real images formed by lens and how they not affect our vision? Like in specs

I have myopia but still why don't I see diminished images. I tried many YouTube videos wherein I have found how real images in mirror are of no practical use but yet they are visible ....with lens I ...
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### Variations of thin lens formula [duplicate]

I came across the thin lens formula online as: $$\frac 1f = \frac 1v + \frac 1u$$ where f = focal length, v = distance of image, and u = distance of object However, I noticed that the formula was ...
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### Why can I see inverted image of object needle on top of image needle using convex lens on optical bench?

Basically what the question says. Convex lenses form images that are real and inverted and obtained on a screen unless the object is placed extremely close to the lens. So why am I able to see an ...
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### Optics to image laser reflection on sensor

I'm a software dev dabbling in laser optics and I'd like to use lenses to project a laser reflection onto a sensor strip. I know how this works in principle, but I have no idea what sort of lenses I ...
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### Question about obscura eye lens

Assume I have some contact eye lenses which I covered with black color, so they're not transparent anymore. Then I made a tiny hole at the center of each eye lens. What kind of an image will I see if ...
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### What are these stripes in swimming pool light lenses called which make the LEDs seem as if they are pointing towards us, no matter where we are?

What are these stripes in swimming pool light lenses called which make the LEDs seem as if they are pointing towards us, no matter where we are? How do these stripes work? Also, should their angle be ...
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### Telecentric lens has focus point?

I've bought a Computar 55mm telecentric C-mount lens and when I try and use the lens it does not work as I would expect from a telecentric lens. First of all I can vary the distance between the two ...
1 vote
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### What is the beam divergence of a defocused point source collimator?

It is widely known that placing a converging lens in front of a collimated light source focuses all light into a point @ $d=F$, and that the inverse occurs: a point source at the focal length of a ...
1 vote
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### Objective lens and Eyepiece of a compound microscope

Why is the objective lens always powerful than Eyepiece of a compound microscope? Will it not work if Eyepiece is more powerful? In a book it is given that Eyepiece has larger focal length.
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### Determining the Focal Length of a Convex Lens

So yesterday, we did a practical in Physics, where we found the focal length of a convex lens, through an experiment where we had 2 needle-like objects and a convex lens placed between them, and we ...
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### Thin lens equation when the image distance is equal to the focal point of a convex lens

I'm not very knowledgeable in optics but i'm learning about lens and the thin lens equation: $\frac1f = \frac{1}{d_o} + \frac{1}{d_i}$ and was wondering about a specific problem that i'm reading. It's ...
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### Trinocular optical ray tracing reference

I am new to the optical tracing, was looking for ray tracing refence that shows what kind of lens used in trinocular optical train. Most what is out there is an explnation of microscope theory and ...
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### What is the angle of a ray passing through a thin lens?

Let's say I have a thin lens model of an optical system. When I have a ray that is parallel to the optical axis, the situation is quite standard - the ray refracts and passes the focal point f (see my ...
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### 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 ...
1 vote
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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 ... 48 views

### 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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### 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 ...
1 vote
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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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### 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 ...
1 vote
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### 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 ...
1 vote