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. N

    How Do You Calculate the Focal Length and Placement of a Projection Lens?

    The projection lens in a certain slide projector is a single thin lens. A slide 20.0 mm high is to be projected so that its image fills a screen 2.0 m high. The slide-to-screen distance is 3.00 m. (a) Determine the focal length of the projection lens. (b) How far from the slide should the...
  2. N

    Converging Lens Problem: Finding Distance from Slide for Real and Virtual Images

    A transparent photographic slide is placed in front of a converging lens with a focal length of 2.24 cm. The lens forms an image of the slide 11.4 cm from the slide. (a) How far is the lens from the slide if the image is real? (b) How far is the lens from the slide if the image is virtual...
  3. R

    Identifying Converging and Diverging Lenses: Explaining with Principal Rays

    I got a problem where it gives us a diagram with a lens, a source and a image. We have to draw the three principal rays. But after drawing the rays, how can I tell if it is a diverging or converging len? And how can I explain it verbally? Thanks a lot!
  4. P

    Is the Lens of the Eye Living or Non-Living? Explained

    i just want to know, does the lens which present in the eye consider as living or non-living ? please can u provide me with a proper explanation. thenk you
  5. F

    News Viewing the SDI through a political lens

    To look at the SDI through a scientific lens, one can formulate a lot of arguments for and against its legitimacy. However, to what extent do you guys believe that Reagan's Strategic Defense Initiative brought about the end of the Cold War?
  6. J

    Solving for Equal Image and Object Height on the Principle Axis | Optics Problem

    Hi my teacher assigned a few challenging optics problems, I got most of them but I am stuck on this one.. "Find a position on the principle axis that will ensure |hi| = ho ". When is the height of the image equal to the height of the object? How would I go about solving this?
  7. D

    Rotating Lens for optimal viewing

    Rotating microscope lens I have a question regarding spinning clear lens's on microscopes. If you spin a lens at a great velocity will it somehow refract light/electrons that comes up from below allowing for a better image of say any object on a slide for viewing ? In...
  8. T

    Can Ice Act as a Converging Lens to Start a Fire?

    Converging lens made of ice Would it be possible to start a fire by shaping a piece of ice ? That's the question. I'm thinking that yes it would be possible if you shaped the ice in the form of a converging lens. Even though the lens is made of ice, the sun rays would not burn through it...
  9. W

    Liquid Crystal Contact Lens: The Future of Vision Correction?

    Would it be possible that Opticians will be selling to visually impaired people, Contact Lens, made from a material that has a negative index refraction, that theoretically could be altered with a Liquid Crystal "Eye-Drop" solution? Basically how far are we from a Liquid Crystal Contact Lens...
  10. K

    Thin Lens Exp: Prove Linear Graph, Determine Slope and Intercept

    Hi, I'm first year Engineering in the Phys1130 course at my college and I've ended up hitting a large brick wall with the pre-lab. The pre-lab section of the experiment goes: "The thin lens equation is: (1/do) + (1/di) = (1/f) di = distance from lens to image do = distance from...
  11. S

    Converging Lens Magnification Problem

    What am I missing here? A person looks at a gem using a converging lens with a focal length of 15.0 cm. The lens forms a virtual image 26.0 cm from the lens. Determine the magnification. (1/p)+(1/q) = (1/f) p=? q=26 cm f=15 cm (1/15)-(1/26)= Ans^-1 = 35.5 cm (p) Magnification=...
  12. K

    Optical Lens and Sensor Setup: Detecting Magnified Images

    im in a slight fix. i am presently using a light sensor. i was asked to use a lens along with it recently. is it because the obect i am going to sense is magnified by the lens so that sensor can detect it easily? but, let's take the situation where a real image is formed because of the lens...
  13. K

    Does Using a Lens with a Light Sensor Enhance Object Detection?

    im in a slight fix. i am presently using a light sensor. i was asked to use a lens along with it recently. is it because the obect i am going to sense is magnified by the lens so that sensor can detect it easily? but, let's take the situation where a real image is formed because of the lens...
  14. S

    Converging and Diverging Lens Problem: Finding the Focal Lengths"

    I am having some trouble with this one...any help would be appreciated. A 31.8cm focal length converging lens is 21.6cm behind a diverging lens. Parallell light strikes the diverging lens. After passing through the converging lens, the light is again parallel. What is the focal length of...
  15. H

    Converging lens and Concave mirror

    A converging lens (convex) and a concave mirror, both of focal length 5.0 cm, are arranged with their axes in line. The lens and the mirror are 10.0 cm apart and a candle is placed 3 cm infront of the mirror. By using a ray diagram or some other metho, find the location of all the images...
  16. N

    How can we find the focus in a lens

    how can we find the focus ?thanks
  17. M

    How Do You Calculate Focal Length in a Lens Lab Experiment?

    In my physics lab, we have been assigned to find the focal length of a lense that was given to us. The professor says it can be found by using this formula: Object distance over 1 plus 1 over the Image Distance will equal one over the Focal Length. So, we put a piece of white paper at ground...
  18. E

    Locating Object & Image with a Converging Lens

    1) Aconverging lens with a focal length of 7 cm forms an image of a 4 mm tall real object that is to the left of the lens. The image 1.10 cm tall and erect. Where is the object located? Where is the image located? 2) A converging lens with a focal length of 12 cm forms a virtual image 5 mm...
  19. G

    Experience Realistic Lens Simulation with Our Convex Lens Program

    Convex Lens How about this simulation program How about this ?>
  20. M

    Solve Lens Problem: Focal Length & Magnification

    Lens Problems problem 24. A person looks at a gem using a concverging lense with a focal length of 13.7 cm. The lense forms a virtual image 35.5 cm from the lense. a) Find the magnifaction. This is what I have done so far: f=13.7 , q= -35.5 1/p+1/q=1/f 1/f-1/q=1/p...
  21. M

    Finding Magnification of a Gem Using a Converging Lens

    problem 24. A person looks at a gem using a concverging lense with a focal length of 13.7 cm. The lense forms a virtual image 35.5 cm from the lense. a) Find the magnifaction. This is what I have done so far: f=13.7 , q= -35.5 1/p+1/q=1/f 1/f-1/q=1/p...
  22. J

    Solving a Camera Lens Problem: Height of Image on Film

    i need some help with this problem anyone want to give it a shot? thanks A camera is supplied with two interchangeable lenses, whose focal lengths are 35.0 and 150.0 mm. A woman whose height is 1.80 m stands 10.00 m in front of the camera. What is the height (including sign) of her image on...
  23. K

    Where can I find resources to grasp lens reflections?

    Anyone know of a place I can go to help me understand lens reflections?
  24. L

    Diffraction limit on resolution on camera lens

    Spy planes fly at extremely high altitudes (24.0 km) to avoid interception. Their cameras are reportedly able to discern features as small as 5.48 cm. What must be the minimum aperture of the camera lens to afford this resolution? (Use lambda = 550 nm.) This problem is unfamiliar to me, I'm...
  25. D

    Diverging Lens and Concave Mirror

    Can someone get me started on this, I know how to work a diverging lens and a concave mirror, just not together. The problem: A concave mirror with a radius of curvature of 20.0 cm is placed 25.0 cm from a diverging lens with a focal length of 16.7 cm. An object is placed midway between the...
  26. C

    Solving Light Lens Problems: Find Position & Magnification

    I have two questions that i couldn't do, it aint that hard: 1.An object is placed 30.0cm from a convex lens of f=10.0cm. Find the position and the magnification of an image. (f = focal length) An object is placed 20.0cm from a convex lens of f=30.0cm. Find the position and the magnifying...
  27. C

    Light Lens Help: Questions on Position & Magnification

    Can anyone help me on these 2 questions? 1.An object is placed 30.0cm from a convex lens of f(focal length)=10.0cm. Find the position and the magnification of an image. 2. An object is placed 20.0cm from a convex lens of f=30.0cm. Find the position and the magnifying factor of an image...
  28. H

    Troubleshooting My Discman: Lens Smudged or Something Else?

    My discman has stopped working recently. When I put a CD in and push play, the disc spins for a while and eventually the display reads "No Disc." It occurred to me that maybe my discman isn't recognizing CDs because the lens is smudged, but I'm not sure. Any advice? Should I shell out some money...
  29. P

    Diffraction lens diameter Problem

    Tried this problem for about 2 hrs and no dice... A spy satellite orbiting at 150 km above the Earth's surface has a lens with a focal length of 3.5 m and can resolve objects on the ground as small as 36 cm; it can easily measure the size of an aircraft's air intake. What is the effective...
  30. J

    Compute the focal length in air of a thin biconvex lens

    Compute the focal length in air of a thin biconvex lens (n=1.5) having radii of 20 and 40 cm. Locate and describe the image of an object 40cm from the lens. my answer: 1/f = (n-1)(1/R1-1/R2) 1/f = (1.5-1)(1/20-1/40) 1/f = .5(.025) f = 1/.0125 = 80cm (convering lens because f is...
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