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.

View More On Wikipedia.org
Recent contents Top users
  1. C

    Concave Lens _ Image Formation

    A concave lens always forms a virtual image (for a real object), will it always form a real image for a virtual object? (that is, when rays converge on it) If yes, why? If no, why?
  2. K

    What Focal Length Lens Corrects a Near Point from 80cm to 30cm?

    Homework Statement A person had a near point of 80 cm. What focal length lens would be required to correct this persons near point to 30cm, allowing then to read at this distance Homework Equations Maybe: 1/di + 1/do = 1/f = P I found another similar question which used 1/(the...
  3. L

    Refraction through a thin lens

    Homework Statement A lens is a transparent refracting medium bounded by two spherical surfaces.R1 and R2 are radii of two surfaces. Homework Equations Will the Radii R1 and R2 will be same or different ? The Attempt at a Solution I hope that they are same, otherwise there won't...
  4. L

    How Does Lens Separation Affect Image Distance in a Dual Lens System?

    Blanking quite a bit on this one Homework Statement Assuming that paraxial light from a distant object enters lens 1, find the image distance s′2 (due to the refraction at lens 2) as a function of the lens separation d. Your answer will also contain f, the unspecified focal length of the...
  5. S

    Lens problem with another medium of refractive index =2

    [SOLVED] I have got the answer. Answer is 40cm. --------- Homework Statement Focal length of thin lens in air is 10 cm.now medium of one side of lens is replaced by medium of refractive index μ=2.the radius of curvature of lens with contact with the medium is 20cm. Find the new focal...
  6. M

    Convergin and divergent lens, rare situations

    what happen if converging rays are made to pass to a convex lens? what happen if divergent rays are made to pass to a concave lens?
  7. C

    Finding final image through a lens

    Homework Statement An object is situated at various points relative to V. The light is then reflected by the mirror, and the final image is viewed by the observer. http://www.flickr.com/photos/55153239@N03/6196518731/ Homework Equations 1/s + 1/s' = 2/R na/s + nb/s' = (nb-na)/R...
  8. X

    How do I calculate magnification using multiple gravitational lenses?

    Hi, I've been working on a problem involving gravitational lens, and right now I'm trying to learn the formula to calculate magnification of light due to multiple gravitational lens. I've gotten to an equation that I've become stuck on. I've been using formulas from this paper...
  9. M

    What happens if eye lens and objective lens are interchanged in

    What happens if eye lens and objective lens are interchanged in compound microscope? Also what about in astronomical telescope?
  10. J

    Focus of Lens Submerged In Water

    Homework Statement A glass lens (n=1.50) in air has a power of +5.2 diopters. What would its power be if it were submerged in water?Homework Equations Not too sure. May be Lensmaker's Equation, Snell's Law, and Power of a Lens Equation.The Attempt at a Solution I'm trying to derive the...
  11. J

    Newtonian Form of Lens Equation

    Can the Newtonian Form the Lens Equation f=x'x be derived directly from the standard form the lens equation? \frac{1}{f}=\frac{1}{d_{i}}+\frac{d}{d_{o}} x is the distance between the object and the focus on the same side of the object. x' is the distance between the image and the focus on the...
  12. P

    How big should a lens be to focus enough light to reach 1000 Celcius?

    How big should a lens be to focus enough light to reach 1000 Celcius? I was wondering how big should a glass lens be to focus enough light to produce a temperature of about 1000 celcius at its foci? What if the lens was made up of sth with higher refractive index, doesn't this reduce the...
  13. E

    Trying to find the image of an object reflected through a lens and

    then through a plane mirror (I could put that all down in the title!) Homework Statement A bright object 1 cm tall is located at x = -6 cm. There is a thin lens atx = 0 with focal length f = 4 cm, and a plane mirror located at x = 7 cm. Light from the object passes through the lens, reflects...
  14. Y

    Difference between convex lens formula and convex mirror formula

    Homework Statement difference between convex lens formula and convex mirror formula The Attempt at a Solution for convex mirror you make focal point negative and use the 1/f = 1/do + 1/di but for convex lens do you do the same? you don't make the f negative i think am i...
  15. F

    Calculating Focal Length and Image Height of a Lens

    Homework Statement A lens forms an image of an object. The object is 16 cm from the lens. The image is 12 cm from the lens on the same side as the object. (a) What is the focal length of the lens? Is the lens converging or diverging? (b) If the object is 8.5 mm tall, how tall is the image...
  16. C

    Distance Between Lenses for a Magnification of 10

    Homework Statement A convex lens and a concave lens both of 6cm focal length are placed to give an object which is 5cm from the convex lens of magnification of 10. How far are the lenses apart? Homework Equations 1/f = 1/u + 1/v Magnification=v/u The Attempt at a Solution Lens...
  17. P

    Focal Length Calculation for a Converging Meniscus Lens

    A converging meniscus lens has an index of refraction of 1.55 and radii of curvature for its surfaces of 6.00 cm and 11.0 cm. The concave surface is placed upward and filled with carbon tetrachloride which has n = 1.46. What is the focal length of the glass combination? So I tried using the...
  18. A

    Why Does Tube Length Affect Microscope Focal Length?

    I am trying to design a microscope and I am confused about some concepts. I plan to buy a Olympus 4x infinite-corrected objective lens and 6 inch long tube and a tube lens (f= 75mm) and then a CCD camera. By chance I found a tutorial online...
  19. zimo

    A lens and a convex mirror problem

    Homework Statement A body is positioned 40 cm from the left of a lens (f=30) and the lens is positioned 100cm left of a convex mirror (|R|=60), where will be the image and what type and magnitude will it have? Homework Equations 1/u + 1/v = 1/f The Attempt at a Solution I tried to...
  20. S

    Concentrating radiation from blackbody with lens

    1)Is it possible to concentrate infrared radiation from a blackbody with a lens? 2)Should a lens be at different temperature from a blackbody?
  21. AXidenT

    Astronomical Lens Telescope Problem - Angular Magnification

    Homework Statement A convex lens forms an image 8.96 mm on a screen. Keeping the screenand the object fixed, the lens is moved through a distance of 15.4 cm and a sharp image of the object is again observed on the screen. If the length of the second image is 3.54 cm, calculate the focal length...
  22. I

    Solving the Concave Lens Problem for a Hotel Room Peephole

    A certain 0.86 cm lens is used in a peephole for hotel room doors for safety reasons. The tenant sees the maid in the peephole but she is reduced in size by a factor 0.01. A. What type of lens must be used? B. Where is the image of the maid located? C. What is the power of this lens...
  23. I

    Diamond Ring in Front of a Convex Lens?

    Homework Statement A 1.5 cm high diamond ring is placed 20 cm in front of a convex lens whose radius of curvature is 30 cm. a) What is the position and the size of the image? b) What magnification does this lens have? Homework Equations 1/f= 1/di + 1/do m= -di/do or hi/ho The Attempt at a...
  24. A

    Ray Tracing and Lens Formula for Image Location

    Homework Statement An object is locted 15cm infront of a convae lends with a focal length of 10cm. use ray tracing to determine the location of the image. try to draw to scale i)is the image upright or inverted? ii)is the image real or virtual? iii)use your ray-tracing diagram to...
  25. L

    Solve Lens Equations: Object 8cm @ 80cm, Focal Length 25cm

    Hi, I need someone to outline how to get the solution of the problem which is: An object 8.0 cm high is placed 80 cm in front of a converging lens of focal length 25 cm. Calculate the image position and height. Thanks, Eric
  26. D

    Finding Convex Lens Focal Length

    Homework Statement Following data recorded: Di (distance image to lens) 6.0 8.0 10.0 12.0 14.0 Magnification 0.2 0.6 1.0 1.4 1.8 Graph magnification against di and use the graph to find the focal length of the lens. Homework Equations...
  27. T

    Concave Mirror Problem: Finding Image Distance, Height, and Magnification

    1. Homework Statement - A concave mirror with a focal length of 4.7cm has a 1.8cm object 9.4cm in front of it and i need to know the distance, height, and magnification of the image also i need to figure out how to locate the image by drawing a ray diagram 2. Homework Equations - all i...
  28. B

    Does Lens Design for CMOS Cameras Require Knowledge of Wave Optics?

    Hello, I would like to ask a question on lens design. My goal is to design a lens for CMOS cameras and the objective is: shooting things at 2cm near magnification ratio is about 1/2 completely monochromatic I was wondering does designing lens like this involve any knowledge on theoretical...
  29. G

    Calculating the Volume of a Concave Lens Using Multiple Integration

    Homework Statement A circular concave lens of radius 2 units, has two refracting surfaces described by z=1/2(x2+y2+1) and z=-1/2(x2+y2) What is the volume of the glass? Homework Equations Over a region R: V=\int\int\int dA The Attempt at a Solution I have no idea how to start...
  30. B

    Optical Lens Design Forum: Tips & Resources for Beginners

    Hi, Does there exist any form for optical lens design? I am a beginner in this field and would like to find such forum, and have search physicsforums.com, but only found isolated threads without any dedicated subforum. Bob
  31. V

    Designing a special wide angle lens

    Hello, I have a specific application where I need a custom lens designed to focus an image onto a very small cmos image sensor. So far, I've figured out the general angles of the lense but I need it to be a perfect design before money is put into prototyping it. Here's the specs: The image...
  32. S

    Fundamental Group of lens space

    Hi i want to see why the fundamental group of lens space L(p,q) is Z_p. Can you help me?
  33. K

    Optics: distance b/w lens & slide

    Homework Statement The picture of a tree on a 35 mm color slide is 1.7 mm high. It is to be projected onto a screen 8.0 m from the slide, and is to appear 559 mm high. a) What focal length lens (in meters) is needed? b) What is the distance in meters between the lens and the slide? c)...
  34. S

    Why Is an Image at Infinity Called Highly Magnified?

    When an object is placed at the focal point of a convex lens, the image is formed at infinity, yet it is called a highly magnified image. The fact being that after passing through the convex lens the rays run parallel or rather as a beam. My question is that if the image is formed at...
  35. H

    Laser Split Into Camera Lens Pattern: What is it?

    What is the pattern made of balls? https://www.youtube.com/watch?v=KrUhKQxOPx0 I have some hypotesis: Something related to the CCD, a diffraction pattern caused by some dirt on the lens, or, but i think it's absurd, the Bravais lattice of the lens? I'm very curious!
  36. T

    Problem concerning zoom lens in camera

    Problem concerning zoom lens in camera... This problem deals with a diverging lens placed to the right of a converging lens. The converging lens has a focal length of 12cm and the diverging lens has a focal length of -12cm. The lenses are separated by 4cm. a) For a distant object, where is...
  37. L

    Solving a Virtual Image Problem Involving a Converging Lens

    Homework Statement A converging lens of focal length 0.246 m forms a virtual image of an object. The image appears to be .933 m from the lens on the same side as the object. What is the distance between the object and the lens? Homework Equations 1/f = 1/di + 1/do Since the image is...
  38. D

    Infinity corrected lens - expanding before tube lens?

    Hello folks, I am on a project that involves combining Raman microscopy + optical tweezers, and I made a setup over the past year. All of this is home built on minimal funds so its not the neatest of all setups. It involves an upright microscope (coupled to trapping laser) and collecting the...
  39. T

    Optics problem involving a converging lens

    Homework Statement An Object and a screen are located a fixed distance D apart. (A) Show that a converging lens of focal length F placed between the object and screen will form a real image on the screen for two positions that are separated by a distance d=(D(D-4F))^1/2 (B) Show that...
  40. A

    How Is Magnification Calculated with Two Thin Lenses?

    Homework Statement A light source placed in the focus of a (thin) lens with a focal length of 50mm. A second (thin) lens (with focal length = 400mm) was placed 600mm after the focal point of the first one, an image of the light source was captured at the seonds lens focal point. How...
  41. F

    Gaussian Beam focusing with lens

    Homework Statement Find the condition needed for a gaussian beam with waist a distance d0 from a thin lens to be imaged (so its geometric image is at di from the lens as per 1/f=1/di + 1/d0) so that its new waist occurs at di, the geometric image position. Homework Equations...
  42. R

    How Do You Calculate Image Size and Location with a Diverging Lens?

    okay the problem reads -an object 3 cm tall is placed 16 cm in front of a diverging lens with a focal length of 24cm. Find the location and size of the image. What kind of image is it? 1/f = 1/di+1/do hi/ho = di/do I'm not to sure how to solve this i used the equation; 1/f =...
  43. C

    Getting the hubble constant from time delay in a gravitational lens

    Homework Statement I am working on a project for my cosmology course. I need to determine the Hubble constant from time delay in a gravitational lens. We are using QSO 0957+561 for our data. My question is how do I determine the relevant distances Dl, Ds? I have Dls already. The...
  44. C

    Getting the hubble constant from time delay in a gravitational lens

    Hi everyone, First time posting, sorry if this is in the wrong format or wrong place. For a project in a cosmology course I need to find the Hubble constant from from time delay in a gravitational lens. the one we are using is QSO 0957+561. My question is how to I find the time delay from...
  45. M

    How does the human eye lens work?

    Ok, I know that the human eye lens adjusts its focal length depending on the object distance to obtain a sharp image on the retina because the image distance has to remain constant. What I am not able to understand is how do the ciliary muscles and the suspensory ligaments contract in order...
  46. P

    An optics problem - elliptical lens and plane waves

    Homework Statement I must show that a point source placed at one of the focii will produce a plane wave (or vise versa) when the light is refracted through the interface. This problem is really kicking my ***, I've spent at least three hours trying to figure out different ways to do it...
  47. P

    Why Do Sunglasses Have Zero Power?

    I have an interestng question. Though sunglasses have curved surfaces-why they have zero power? Can u answer me?
  48. W

    Calculate Lens Focal Length - Convex & Concave Lenses

    Homework Statement I have an actually interesting practical homework. I need to calculate the optical strength (hope I translated it right, D=1/F), to do I need to find the lens focal length. I need to find my self a concave and a convex lens. I don't have a concave lens (I think), but I do...
  49. M

    Ray Diagram: Small Bulb & Convex Lens

    Homework Statement A small bulb is placed in front of a convex lens. a) Suppose that the bulb is placed as shown. Using all three principal rays, draw an accurate ray diagram to determine the location of the image. Label the image location...
  50. O

    Deriving Focal Length for a Thick Lens

    Homework Statement Derive 1/f = (n-1)*( (1/r1)-(1/r2)+(((n-1)t))/(nr1r2))) using the ray matrix method. Homework Equations Matrix for curved dielectric interface: M1 = [1, 0] [(1/r)(n1/n2 - 1), n1/n2 ] Matrix for translation through homogeneous medium: M2 = [1, d] [0...
Back
Top