What is Lenses: Definition and 320 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. M

    Algebraic Explanation of Image Formation in Convex Lenses

    Homework Statement An object is in the focal length of a convex lens. As the object is moved from the focus towards the lens, what happens to the object? Homework Equations 1/f=1/d0+1/di The Attempt at a Solution I know how to solve this problem using ray diagrams, and the solution is: The...
  2. W

    Question based on Lenses -O level/gcse

    Hey can anyone explain this question to me?
  3. Andy Resnick

    Insights New High Performance Ultra-wide Angle Lenses - Comments

    Andy Resnick submitted a new PF Insights post New High Performance Ultra-wide Angle Lenses Continue reading the Original PF Insights Post.
  4. Toby_phys

    Compound lens separated by a distance

    Homework Statement Homework Equations We will call ##s## the distance of the object from the first lens, ##s'## the distance of the image from the first lens and ##s''## the distance of the image from the second lens. The Gauss's lens equation: $$\frac{1}{s} +\frac{1}{s'}=\frac{1}{f_1}$$...
  5. A

    Lenses often contain thin coatings to reduce reflections....

    Homework Statement Lenses often contain thin coatings to reduce reflections and UV radiation. Explain how this works. Homework EquationsThe Attempt at a Solution To reduce reflections on lenses, known as back-glare, they are often coated in what is called anti-reflective (AR). The AR causes...
  6. heavystray

    Invisibility cloaking using 4 lenses

    Hello, So, here's an article about invisibility cloaking http://www.businessinsider.my/how-to-make-a-rochester-invisibility-cloak-2014-9/?r=US&IR=T#ruDbxWBJYWXsXcyW.97 What I don't understand is how's the object between the lenses is cloaked. Is it because the rays are focused to a point...
  7. tensor0910

    Two lenses: find Di through second lens

    Homework Statement A 1.60 cm tall object is 20.0 cm to the left of a lens with a focal length of 10.0 cm . A second lens with a focal length of 36.0 cm is 44.0 cm to the right of the first lens.Homework Equations 1/f = 1/di + 1/do , hi/ho = di/doThe Attempt at a Solution [/B] calculate...
  8. Rheegeaux22

    Help With a Difficult Lenses Question: Find the Answer!

    Homework Statement The question is : https://postimg.org/image/lntyejfvp/ Homework Equations 1/s +1s' =1/f The Attempt at a Solution Hello, I have an upcoming test on Monday on lenses and while reviewing I've come across a question that confused me. My understanding is that the image of...
  9. E

    Trying to buy some simple glass double-convex lenses

    Dear forum, I'm currently trying to buy some simple glass double-convex lenses with no optical coatings from China with the help of a colleague over there. I'm trying to match a lens that I already have but which is no longer readily available to me here in Brazil. The lens I have is...
  10. T

    Absorbed chemicals in contact lenses?

    Dear scientists, I had stupidly put a few boxes of Acuvue Moist Contact lenses together with a plastic bottle of "extra mild dissolvant" (nail polish remover) these stayed in the same bag in a closed cupboard for months before I noticed it. The dissolvant contains Ethyl Acetate, Butyl...
  11. G

    Calculate the focal length of a planoconvex lens?

    Homework Statement Calculate the focal length of a planoconvex lens that produces a real image 2.5 times as big as the object if the object is 2.5 cm from the lens? Homework Equations The only one I can think of is 1/f = 1/v + 1/u The Attempt at a Solution [/B] My 'attempt' is 1/f = 1/62.5...
  12. TheCapacitor

    Why image is blurry or focused with convex lenses?

    Homework Statement I have a few fundamental questions in optics about the focus and blurry images. Each textbook says that according to this picture the object image is the same. 1) If we move the screen to point further then the image will be blurry. What causes it to be blurry? 2) Why do...
  13. TheCapacitor

    Finding focal point of concave lens using concave and convex

    Homework Statement [/B] I was doing http://stao.ca/VLresources/sci-tie-data/lessons/1400_1499/DivergingLensExperimentDeta.pdf experiment. Let's look at this image: Suppose we get the imaginary object at dv by convergence lens. And this object is like a real object for the concave lens. Then...
  14. Y

    Why do convex lenses magnify, and why don't concave lenses?

    So knowing that convex lenses causes light to converge and concave lenses causes then to diverge, why does converging light create a larger image than diverging light? Magnification means we want to see more of a certain part of an object, meaning we want to enlarge that section and have it...
  15. J

    Image Distance with two concave lenses

    Homework Statement An object 1.25 cm tall is placed 100 cm in front of a convex lens with a focal length of magnitude 50 cm. A concave lens with a focal length of magnitude 20 cm is placed 90 cm beyond the first lens. Where is the final image located? Homework Equations (1/s)+(1/s')=1/f s=...
  16. K

    How can I create an adjustable liquid lens system for windows?

    Hi everyone, I am working on a project on my final project in Product design. The project is about translating digital concept into the analogue world. In my project I am especially interested in the digital “Windows” and am trying to apply the functions and possibilities of digital on to...
  17. M

    Help with lenses for hand-made telescope

    I'm trying to make a handmade telescope, but I'm stuck with the lenses I bought 2 lenses. they are the same "convex from one side and concave from the other side" like glasses lenses. then I knew that I need a double convex for both the object lens and the eyepiece lens. so I decided to put the...
  18. T

    Alternative to bifocal and varifocal spectacle lenses?

    Hi Everyone I am not sure but I seem to remember that about ten years ago, I either read something or saw something on TV about a revolutionary new type of lens which could potentially replace bifocal and varifocal spectacle lenses. The main drawback of bifocal and varifocal lenses is that you...
  19. E

    I Identifying the length of the object on the image

    Hello First of all, I was told this is a physics problem. If it's incorrect, I apologize. I have an image I want to know the length of the black ship (the ship which is carrying a ship). Let's assume that I know the length of the text on the ship (I have a reference object). Is this...
  20. W

    Exploring the Fourier Transforming Property of Lenses

    I was reading about this Fourier transforming property of lens,when I came by the experimental setup for Fourier optics(with laser and a 4f correlator system).Part of the setup was that of Fraunhofer diffraction and we get the Fourier transform of the aperture at the focal point of first lens...
  21. A

    System of lenses with a light source at first focal point

    Homework Statement So I have this system of lenses with this problem: First lens: focal length ##f_1=50 mm## Second lens : focal length ##f_2=400 mm## Distance between them ##d=600mm## A small light source is placed at the focal point for the first lens. At the focal point for the second...
  22. L

    The Relationship Between Lens Thickness and Light Convergence/Divergence

    I understand that convex lenses cause light rays to converge while concave lenses cause light rays to diverge. But what is the relationship between the thickness of these lenses and the extent of the convergence/divergence of the light rays?
  23. P

    Equivalent focal length of two lenses

    Homework Statement Two thin lenses have focal lengths of -5cm and +20cm. Determine their equivalent focal lengths when (a) cemented together and (b) separated by 10cm. Homework Equations ##\frac{1}{f_{eq}}=\sum_{n=1}^k \frac{1}{f_n}## The Attempt at a Solution So the first part was easy since...
  24. isnainidiah

    Fermat's Principle to explain lenses and mirrors

    How do we use Fermat's principle of least time to explain the required shapes of lenses and mirrors?
  25. J

    MHB Physics: Images through Thin Lenses

    A thin lenses with given p = 75cm, n = 1.55, r1 = 30cm, and r2 = -42cm. Find the a.) i b.) m c.) Is the image real or virtual d.) Is the image inverted or noninverted e.) Is the image on the same or opposite side as the object Using 1/p + 1/i = 1/f and also 1/f = (n-1)*(1/r1 - 1/r2) I...
  26. I

    Dispersion and the dependences of refractive indexes

    I'm revising for a uni exam with past exam papers, and have gotten stuck on the details of dispersion. The two exam questions prompting this are a) What is the physical reason why the index of refraction for blue light is bigger than that of red light? and b) Explain how dispersion makes a...
  27. Z

    Create DIY Light Intensifier Using Disposable Materials

    1. I am supposed to create a device that can intensify the light directed at a light intensity sensor. A small light bulb will be 25 cm away from the light sensor. My device is required to be 20cm long and placed in between the light bulb and the light sensor in order to make the light that is...
  28. Ibrahim Hany

    Stargazing Problem in making a small refracting Telescope

    It sounds silly to ask such question or stumble in such problem, indeed! But I was willing to make some small telescopes for young friends of mine, to encourage them to delve in the skies. So, I bought: 1. Double concave, spherical glass lens, with a focal length of approx. -75mm and diameter...
  29. C

    Object Distance for Mirrors versus Lenses

    We are finishing up light and I'm a little confused on when the object distance would be negative when we are talking about mirrors and not lenses. The definition we were given is that the object distance is negative if the incoming light is on the opposite side of the mirror then the object is...
  30. Qiao

    Fourier optics with concave (diverging) lenses

    Hey, I was wondering, since for a convex lens the Fourier transform of a fields is in their real focus plane. Is it for a concave lens that the Fourier transform of a field is in the virtual focus plane? I can't find any book or paper that talks about how concave lenses work in terms of...
  31. E

    Exploring Real & Inverted Images with Bi-Convex Lenses

    Homework Statement An object is placed between the optical centre and the focus point of a bi-convex lens. The image obtained is always inverted and real. Is this statement true? Justify your answer using the thin lens equation. Homework Equations The Attempt at a Solution
  32. V

    Specification Required for Pathology Microscope lenses

    Can someone tell me the specs of the pathology microscope lenses both objective and eyepiece/ocular lenses . Objective lenses magnification are as follows; 10X 45X 100X Eyepiece lenses magnification are as follows; 15X 10X Specifications should mention details about their Focal length Radius of...
  33. DrewHizzy

    Diverging and Converging lenses in a system

    Homework Statement A)Find the final position of the image (from the object, I assume?) B)Find the size of the final image of the object. Homework Equations 1/f = 1/do + 1/di The Attempt at a Solution 1) Solved first distance: 1/5 - 1/4 = 1/di --> 4/20 - 5/20, di = -20cm 2) Use di1 for do...
  34. J

    Ray Tracing - Optics - Bend light with circular lenses

    Hey guys first time poster. I have written a 2D ray tracer in Mathematica. It's very basic, all it does is use Snell's law to trace ray refraction and very basic absorption. The set up is a central absorbing circle surrounded by circular lenses. The central circle is a perfect absorber, so if a...
  35. 2

    Engineering Book on lenses, their types, properties, etc.

    Specifically I am interested in a book which talks about lenses, their types, where and how they are used. How do binoculars, telescopes work (how to construct them), what type of lenses to use... Am I asking for too much? Would really appreciate if any of you guys could suggest me of such a...
  36. R

    Focal length of 2 lenses to reduce laser beam diameter

    I need to reduce the beam diameter of a laser I am using. I plan to do this by first passing the beam through a positive spherical lens with focal length f1 and then a negative spherical lens with focal length f2 and f2 < f1. By placing the lenses so that the two focal points overlap I will have...
  37. R

    Lenses Question -- image is to be the same size as the object

    Homework Statement At what distance from an object must a 55mm camera lens be placed if the image is to be the same size as the object? Homework Equations 1/u + 1/v = 1/f m = v/u do/di = ho/hiThe Attempt at a Solution My thinking is that (m) needs to equal 0 therefore v/u needs to equal...
  38. Fallen-S36

    Bending the Rules (Gamma ray lenses)

    http://news.sciencemag.org/sites/default/files/styles/thumb_article_l/public/article_images/sn-gammarays.jpg?itok=vYTMw8My Researchers at Institut Laue–Langevin have found a way to bend gamma rays. Gamma ray lenses, which theory had suggested were impossible, could be made from heavy elements...
  39. L

    Electrically Controlled Auto Darkening Lenses: Mirrored or Transparent?

    The technology of electrically controlled auto darkening welding lenses wherein the lens protects the welders eyes by transforming from clear to opaque within milliseconds is fascinating. I would ask, is anyone aware of a lens that is electrically controlled but produces a mirrored surface...
  40. Z

    Lens Question for Design of an Infrared Spotlight

    Hello All. I'm working on a project to build an infrared spotlight which will hopefully light up a distant object so that I can see it on an IP enabled night vision camera. The lens problem seems very straight forward, but I could use some help. Per the attached diagram, I want to focus the...
  41. M

    How Is Object Distance Calculated in Mirror and Lens Equations?

    Homework Statement In front of a spherical concave mirror of radius 39cm, you position and object of height 0.6cm somewhere along the principal axis. The resultant image has a height of 0.2cm, How far from the mirror is the object located? What if this were a convex mirror with the same radius...
  42. gracy

    Are Contact Lenses Safe for Your Iris? A Look in the Mirror.

    Are contact lenses worn on (fully cover)the iris?If yes,then can iris get damaged or at risk in any way while wearing contact lenses?And how iris function is being performed when contact lenses are put on them?
  43. T

    Calculating Thickness of Lenses for Max. Reflection: n1, n2, λ

    Homework Statement A highly reflective mirror can be made for a particular wavelength at normal incidence by using two thin layers of transparent materials of indices of refraction n1 and n2 (1 < n1<n2 ) on the surface of the glass ( n>n2 ).(Figure 1) A)What should be the minimum thicknesses...
  44. J

    Can't find any micrograph for glass

    I can only find micrographs (photographs of microstructure under electron microscope) of non-transparent glasses. Is it impossible top be able to see the internal structure of a transparent material? If anyone can tell me what I'm doing wrong or find me one that would be great! I'm looking...
  45. Choisai

    Microscope magnification with camera

    I have two lenses for my microscope. The object lens which magnifies 63 X. Then there is my eyepiece lens with f=100 mm which focuses the incoming light at an camera. How can I calculate the total magnification? All calculations so far for the eyepiece involve the 25 cm of the human eye, but now...
  46. S

    Diverging and Converging Lenses

    Homework Statement A diverging lens (f = –13.0 cm) is located 18.0 cm to the left of a converging lens (f = 31.0 cm). A 3.30-cm-tall object stands to the left of the diverging lens, exactly at its focal point. Determine the distance of the final image relative to the converging lens Homework...
  47. K

    Finding the focal length of a negative lens without another lens.

    Homework Statement A simple method for determining the focal length of a negative lens is shown below. Prove this is true. Homework Equations The Attempt at a Solution The linear magnification formula relates magnification, the distance from the lens to the image (i), the distance from...
  48. P

    Very small holographic laser projectors and diffraction.

    In thinking about what it would take to make a feasible invisibility cloak or holographic disguise or perfect hologram room, I've imagined something that works like this: A light beam "image" is projected onto a device designed to refract or reflect it in all directions, but only 1 color in any...
  49. T

    Question with Three Thin Lenses Calculating for Final Image Distance

    Homework Statement Three thin lenses, each with a focal length of 40.0 cm, are aligned on a common axis; adjacent lenses are separated by 52.0 cm. Find the position of the image of a small object on the axis, 80.0 cm to the left of the first lens. Homework Equations 1/s + 1/s' = 1/f The...
  50. N

    If two lenses have the same radii of curvature but different indexes

    Homework Statement If two lenses have the same radii of curvature but different indexes of refraction their focal lengths won't be equal because the one with the greater index of refraction will undergo greater refraction and will have a smaller f. Doesn't this contradict the definition of...
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