What is Lens: Definition and 830 Discussions

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. Lenses are made from materials such as glass or plastic, and are ground and polished or molded to a desired shape. A lens can focus light to form an image, unlike a prism, which refracts light without focusing. Devices that similarly focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses.
Lenses are used in various imaging devices like telescopes, binoculars and cameras. They are also used as visual aids in glasses to correct defects of vision such as myopia and hypermetropia.

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  1. T

    What are the key considerations for imaging with a condenser fresnel lens?

    Hello All, I am in need of an optics expert on imaging, and in particular a fresnel lens is being used as for an imaging device. From my understanding a condenser lens can be considered equivalent to a plano-convex lens. Setup: A condenser fresnel lens is used, for which both the fresnel and...
  2. physics-james

    Can you make a more focused beam by using convex and concave lens?

    When you put a convex and then concave lens in front of a light source, the light will be parallel but narrower than when it came in such as in a laser beam expander/compressor. Using a pen laser and a convex and concave lens, is it possible to focus the beam by putting a convex then a concave...
  3. R

    A question about different lens setups imaging a rotating stick

    If i put a rotating stick behind lens of several types, so the stick center is behind the lens center, will the stick edges always appear to move at the same rate as areas closer to the stick center?
  4. Ozen

    Ray Diagram for an Experimental Lens Systems

    Hello, I wanted to confirm a suspicion with how the Aimpoint optics work, but to do that I need to do some ray diagrams. I only ever did them with simple convex, concave, and spherical systems while at college. From what I already know of how reflex sights work, the LED is placed at the focal...
  5. K

    Calculate the focal distance of the duplicate

    The picture below shows a so-called chromatic doublet, which is designed to minimize chromatic aberration, ie the wavelength dependence of the refractive index of the glass. The first lens has a flat first surface and a concave second surface with radius of curvature R and index of refraction n1...
  6. Ozen

    Does the Thickness Affect a Semi-Mirror Spherical Lens' Characteristics?

    Hello, I am trying to get a better understanding of optical lens's and came across a question I have not found an answer to. Say you have a lens made of either Polycarbonate or Trivex, and it is a spherical lens. A coating is applied to the side with the smaller radius to reflect certain light...
  7. N

    Image position in an optical system?

    I have an plano-convex lens with focal length 75 mm. The object is 325mm from the lens. a) Where is the location of the image after the lens? b) Where is the location of the image if an beamsplitter is placed after the lens? My solution, questions: a) a = 325 mm b = ? mm f = 75 mmm...
  8. Y

    Engineering Finding the radii of curvature for an achromatic lens

    Since the two lenses are plano-concave and plano-convex, the lens maker equation can be simplified into containing only 1 R for each of the lens. Substituting the values for the red light, I got: 1/f1=0.51/R1 and 1/f2 = 0.64/R2. Adding these two equations and equating them to 1/(500*10-3)...
  9. jisbon

    Plano-convex lens with phase changes

    By drawing arrows, I can find out the following: Since they are in different phases, I get: ##2nt=m \lambda## for dark fringes. In this case, they want me to find the radius of curvature. I'm not sure what to really proceed on here. What I figured out so far is that I will be able to find the...
  10. jisbon

    Single lens creating a diffraction pattern?

    Hi all, So far all the problems I dealt with is dealing with double slits when working with dark and bright fringes. In this case, what should I do in regards with a lens? Also, what does the question mean when it asks for the minimum distance that the lens can resolve on the screen? Does it...
  11. CptXray

    Calculating Resonator Stability with Lens & Mirror

    I guess the resonator will be stable when both focal lengths of lens and curved mirror meet. The curved mirror is fixed and it's focal length: $$f_{curved} = \frac{R_{2}}{2} = 50 \, mm.$$ Then the d should be: $$d=f_{lens}+f_{curved} = 100 \, mm.$$ I think that's also the distance for which the...
  12. B

    Focused Acoustic Shock Wave Device for Generating High Pressures

    I am trying to come up with a design for a device that can generate very high and very brief waves of pressure directed at a 1 mm diameter target (shown as "E" in "Diagram.PNG") housed in a steel support structure "D". The idea is to accelerate hammer "A" towards anvil "B" in a vacuum tube. The...
  13. K

    Find the refractive index for the lens and find the image distance

    A thin lens has an upper radius of curvature 𝑅1 and a lower radius of curvature 𝑅2. When the lens is completely surrounded by air, it has a focal distance 𝑓. The lens is then placed in the interface between air and water inside a vessel (see figure). Calculate the refractive index for the glass...
  14. Kaelor

    Inserting thick lenses into a thin lens system and deducing values

    Homework Statement:: Finding the distance between the back surface of the first lens and the front surface of the back lens. Homework Equations:: 1/f = 1/s_o + 1/s_i I have two positive thin lenses that are separated by a distance of 5 cm. The focal lengths of the lenses are F_1 = 10 cm and...
  15. O

    Diffraction pattern due to a lens with focal length f

    Suppose one light up with a laser on a grid with grid constant g. The grating is followed by a focusing lens with a focal length of f. In the focus (or immediately in front of it) the maxima have a distance d. How large was the distance of the maxima immediately after the grating? scheme: Laser...
  16. M

    Combination lens equation questions

    Homework Statement: Lens questions. Homework Equations: idk Hello, so I was wanting to use a laser beam and purchase a few lens' online for a project and wanted to get something similar to the image below, where i would end with a horizontal light ray i was wondering if anyone knows the...
  17. A

    Understanding a Converging Lens and Its Two Positions

    I am aware that the object would be to the left of the lens and the image would be to the right, but I don't understand what it is mean by " A converging lens of focal length f = 8.96 cm forms a sharp image for two positions of the lens." I don't understand where the two positions would be and...
  18. Lucas Olivio

    Understanding the Mathematical Explanation for Fresnel Lenses

    Homework Statement: what is the mathematical explanation for fresnel lenses Homework Equations: No equations were provided I'm going to post a link to one article I found that I think has the answer, but I couldn't understand because of my lack of knowledge in physics and math...
  19. fernelau

    Understanding the Impact of Convex Lens Focal Length on Water Temperature

    Summary: Hi, I'm doing an assessment for Physics on Optics topics, but I can't really explain how the CV affect the RV CV : Focal length of convex lens RV : Temperature of water after 20 minutes under the sun How I should explain for the temperature difference? 🤔 Please help, Thanks.
  20. D

    I Some redshift from prism effect of a gravitational lens?

    A quick search turned up Simaciu, Ion. (1997). Chromatic aberration of gravitational lens. 10.13140/2.1.1133.6003. The math is beyond me so I first made a basic assumption that chromatic aberration of gravitational lenses worked somewhat analogous to a prism in that red is bent less than other...
  21. DharshanT

    Finding the magnification of a ball lens

    I don't really know how to relate the effective and back focal lengths for magnification purposes. Literature review suggests that a lens of 1mm diameter can have a magnification of 350x-400x, but I don't really know the calculations behind it. Please advise.
  22. jason3w

    Create a focused beam angle of LED light using reflection

    Summary: Will an external surface reflect light into a more focused beam without using a traditional lens? Hey guys. Just trying to focus the light coming from a 1watt LED light source. It's native beam angle is 130 degrees. I'm hoping to focus it to around 30 degrees. We are creating an...
  23. Andy Resnick

    Insights How to Evaluate a Camera Lens for Performance

    Continue reading...
  24. M

    Effects of Lens Element Aberrations on a Fully Corrected Lens Image

    Leitz Summicron 50 is one of the extremelly well corrected lens in the world. Legend says about this lenses internal elements and their spherical aberrations was responsible of lot of beatiful effects on image. For highly corrected lens image , does high internal aberration really effects the...
  25. M

    Controlling light diffraction angle with a holographic "lens"

    I'm a physics student, and working on a class project that requires coming up with a method to control the exit angle (diffraction angle) of a monochromatic light source. For example, taking a laser (monochromatic, coherent light source), spreading the beam, and directing the light at a piece...
  26. J

    Focal length of converging thin lens graphs

    I tried -M=pq = f/(f-p) = f/f - f/p = 1-(f/p) => M+1= -f/p => -Mp-p=f But since it’s the y intercept, p will equal zero and so the focal length will be 0?
  27. navneet9431

    Magnification of an Astronomical Telescope

    My teacher taught me a formula for magnification in case of Compound Microscope, Magnification=(Angle Made By Object On Aided Eye)/(Angle Made by Object on Un-aided Eye) Can I use this formula for calculating magnification of Astronomical Telescope? Thanks!
  28. navneet9431

    B Can we get a real image of virtual objects?

    Is it possible to get a real image of virtual objects, If so please explain with examples and some real life situations? Look at my assertion "rays will not pass through virtual objects so how it can form real image", is this possible, please help.
  29. G

    Calculate the focal length of the spectacle lens

    Homework Statement A hyperopic eye has a near point of 1.10 m. Calculate the focal length of the spectacle lens required to correct the hyperopia (assume that the near point of the normal eye is 25.0 cm.) Homework Equations 1/f=1/p+1/q The Attempt at a Solution I just used .25 m as p and...
  30. P

    What exactly is the thermal lens effect?

    Hello, i just wanted to ask if you can explain to me what thermal lens effect is? I am supposed to answer why laser beam passing through ink or soy sauce creates this effect and i can't find any information on what actually this thermal lens is. I know of course that it is a lens, but why does...
  31. H

    Optical Simple optical lens design help (small projector)

    I need to design a mini projector as a part of a project I am working on. The body of the projector is approximately 7 inch tall and 5 inch wide. I don't know what kind of a lens I need to ensure the projection is sharp and crisp (it is only black and white writing). I know I would need a zoom...
  32. J

    A problem regarding the lens formula

    Homework Statement An arrow of 2cm length stands about 6cm away from a convex lens (f = 2cm). How long is the image of the arrow? Homework Equations - The Attempt at a Solution Whenever I get homework regarding optics and particularly the lens formula, I never really know where to start. I...
  33. Krushnaraj Pandya

    Splitting of a convex lens problem

    Homework Statement A thin convex lens of focal length 20 cm is split into two parts along the principal axis, now there is a 2mm gap between the top and bottom parts, an object O is placed at 10 cm from the lens, the distance between the two virtual images will be? Homework Equations 1/v - 1/u...
  34. N

    The use of plano convex lens in a slide projector

    Hello My question has two parts: 1) Why is plano convex lens used in slide projector? Why can't we use simple convex lens in it? 2) Why are two plano convex lenses used in slide projector? Why can't we use only one?Thanks!
  35. A

    B What easily avaible liquids are transparent in IR?

    Hi I want to make a infrared nonimaging concentrator, but since crystals needed for lenses are difficult to work with for an amateur, want to use liquids. I am interested in the 1-12 micron spectrum; what liquids could i use?
  36. B

    Optics Problem with a Double Lens System

    Homework Statement An object is 25.0 cm to the left of a lens with a focal length of + 15 .0 cm. A second lens of focal length +15.0 cm is 30.0 cm to the right of the first lens. Find the location of the final image and draw it out. Homework Equations 1/f = 1/di + 1/do The Attempt at a...
  37. G

    Equation for the resolving power of a microscope?

    Hi I'm reading through a Quantum Mechanics textbook called Quantum Mechanics by Book by Alastair I. M. Rae and in the opening chapter it talks about the Heisenberg uncertainty principle and talks about how a measurement of position of a particle causes an uncertainty from the momentum due to the...
  38. F

    Double slits and convex lens interference

    Homework Statement Two slits (of width ##a=39 \mu m##) are lighted up with a monocromatic wave of ##\lambda=632,8 nm##. The distance between slits and the screen id ##D=4 m##. The distance between the slits id ##d=195 \mu m##. In front of the slits there are a convergent lens with focal length...
  39. Wolf105

    Lens blanks and glasses frames

    Hey everyone, I've been researching for some time now, and I can' find anything about how the actual lens blanks for prescription eyeglass lenses are made, I've looked on websites like this: http://glassescrafter.com/information/how-prescription-glasses-are-made.html but it only explains how the...
  40. J

    Photoelectric current and a convex lens

    Homework Statement Homework EquationsThe Attempt at a Solution The photoelectric current is directly proportional to the intensity of the light falling on it . It will not depend on the focal length of the lens . When the lens of half the diameter is used , intensity is halved . This...
  41. K

    What is the power of the lens in diopters?

    Homework Statement It is desired to magnify reading material by a factor of 3.5× when a book is placed 9.5 cm behind a lens. What is the power of the lens in diopters? Homework Equations 1/f = 1/di + 1/do M = -di/do P=1/f The Attempt at a Solution I set equal the magnification to -di/do and...
  42. N

    Image with an Plano-Convex lens

    Homework Statement This isn't really a homework, but I am trying to figure out how this would work. I have an plano-convex lens with an focal length of 500 mm. I have an laser source that I like to focus on, to the infinity. I.e. I like to see the laser lobe. Case: What happens to image of...
  43. A

    Simulate other lenses with Time of Flight (ToF) camera

    Hello, I have a small project in which I try to use a Time of Flight camera to detect movement in the Field of View. Now the current Field of View is really narrow (about 25° diagonal FoV), which is we I will have to simulate a bigger one. My professor did try to explain to me what changes...
  44. jishnu

    Should Approved Sign Conventions be Applied in Optics Problems Using Lens and Mirror Equations?

    We have the mirror equation (1/v) +(1/u)=(1/f) and the lens equation (1/v) - (1/u)=(1/f) Where u =object distance from the mirror/lens v =image distance from the mirror/lens f =focal length of the mirror /lens My doubt is, when we are doing some problems in optics using these...
  45. M

    Camera Lens works as a Polarizer or not?

    I read maxwell says electric field polarizes the dielectrics. Does it mean above effect used at photographic camera lens design to make that lens sometimes works like polarizer filter ? Mustafa Umut Sarac Istanbul
  46. Clara Chung

    Deriving the Lens Maker formula of a plano-convex lens using Fermat's Principle

    Homework Statement Homework EquationsThe Attempt at a Solution I only need help on part c. I tried to add up t1 and t2 and differentiate it. However what variables should I differentiate with respect to? If I differentiate with respect to f I got f=root(2) * h, if i differentiate with respect...
  47. Jonforall

    Must we always use absolute value for lens magnification?

    My brother's physics teacher says that magnification and height of image are always positive. Is she right?
  48. shintashi

    Lens Math for a Semicircle and Vesica Piscis?

    Hi, I'm trying to find the way that light (sunlight?) distorts through a lens with a diameter of 1, if the lens has the shape of a semicircle (width of 1/2), and if the lens has the shape of a Vesica Piscis (width of 1/√3). if you need units, yards works. I'm also curious about how that light...
  49. M

    Physics Lens Problem: Find Object Distance

    Homework Statement An object and its lens-produced real image are 2.4 m apart. Part A If the lens has 55-cm focal length, what are the possible values for the object distance? Express your answer using two significant figures. Homework Equations 1/s+1/s'=1/f s-s'=2.4m The Attempt at a...
  50. Altagyam

    Help with optics problem involving diopters

    Homework Statement A nearsighted man uses his ideally prescribed contact lenses that have a refractive power of −3.60 diopters. He would like a prescription for eyeglasses. What is the correct eyeglasses prescription if he wears his eyeglasses a distance of 2.30 cm from his eyes? Homework...
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