Lens Definition and 787 Threads

i need a lens that will make the rays parallel to each other & focal point at infinite.without much loss in the intensity.collimator lens kind of action but not at the cost of intensity.

A convex lens of focal point 0.8m focuses a real image of the moon onto a screen. If the moon subtends an angle of 0.5 degrees to an observer on earth, calculate the size of the moons image on the screen? Thats the question guys, I am really struggling to find the appropriate equation as we...

When you have a biconvex, i.e. two convex lens' back to back, doesn't the light beam just come out straight? Since one convex lens is back to back with another, essentially it is a convex lens, followed by a concave lens. The light would first hit the convex lens, and the light would...

1)Why when a convex lens having radius of curvature R, focal length f and refractive index μ is bisected horizontally along the principal axis its focal length remains the same, whereas when it is bisected vertically focal length becomes 2f? Does the same thing happens in the case of...

Homework Statement Suppose we have a microscope made out of two lenses, both with a focal length of 25mm, placed 36.5mm apart. Find how far in front of the first lens should the object be placed to assure that the image is magnified at least by a factor of 75? One more: Suppose that...

Hello, I have a 12x12" fresnel lens and I want to place a 14mm diameter fiber optics cable at the focal point to transport the light ~2.5 ft. Would there be any heat loss? And what percentage of the light would exit the fiber optics? Thanks, Fritz Laun

1. Why is a telephoto lens considered to have a longer focal length than that of a single convex lens? A lens combination, such as a diverging and a convex lens, is referred to as a telephoto lens. Suggest why a telephoto lens is considered to have a longer focal length than that of a single...

1. Why is a telephoto lens considered to have a longer focal length than that of a single convex lens? A lens combination, such as a diverging and a convex lens, is referred to as a telephoto lens. Suggest why a telephoto lens is considered to have a longer focal length than that of a single...

On a computer simulation (Simion - ion simulating program) I've got two cylinders (with a small gap between them) through which an electron beam goes through. I understand that the "lens" refers to the equipotential lines, since they form a bulge at each end, just like an optical lens. What does...

The BBc just publsihed this story: http://www.bbc.co.uk/news/science-environment-11030889 The conclusion is: "Professor Priyamvada Natarajan of Yale University, a leading cosmologist and co-author of this study, said that the findings finally proved "exactly what the fate of the Universe...

Homework Statement The lenses are separated by 250mm. Where should the object be places so that the final image is formed at infinity? I'm confused.

Eyes and cameras - a topic that has been troubling me Hi all. This is my first post. I'm seriously thinking about applying to optometric college in the fall. I'm trying to improve my knowledge as much as possible of the area, and one question that keeps coming up (I'm a hobby photographer...)...

Hello, all, I am using 9 fresnel lenses (~1x1' per lens) and 9 water blocks for a solar water heater. Each fresnel lens is positioned so that a water block below is heated. A pump is used to pump the water through the system. However, I have one question... I have all of my fresnel...

I'm designing a flashlight using a new LED reflector. It creates a good spot, but I want it to flood on the edges. See image below. My thought was to create a lens and put it in front of the LED reflector to disperse the light around the edges. Can anyone point me to some simple tools that will...

I'm having difficulty understanding how to estimate the location of an image in a lens/mirror. I tried understanding it by going off the books question/answer section: "A spherical concave lens has a focal length of 16 cm, and an object is placed 8 cm from the lens." It says the answer is...

Homework Statement A slide projector needs to create a 81 cm high image of a 2.0 cm tall slide. The screen is 360 cm from the slide. Assume that it is a thin lens. What focal length does the lens need? How far should you place the lens from the slide? Homework Equations 1/f = 1/s +...

Homework Statement Two Lens systems: Lens one is a diverging lens and lens two is converging O1 (object distance) = 9.6 cm Focal length F1= 6.5 cm distance between the two lenses is 13 cm F2 = 7.4 cm Find the image distance i2 for the image produced by lens 2 (the final image...

Hello everyone, I am a software engineer and know very little about lenses but am trying to learn. I am confused about the differences between convex-convex and plano-convex and how to decide how to design an actual plastic lens for a real world application. Here is an example (not real...

Homework Statement Which of the following diagrams involves a larger image? Homework Equations The Attempt at a Solution I believe its the image with the mirror.

Homework Statement Can a converging lens in air become a diverging lens in a different refractive medium? Homework Equations n1sin(θ1)=n2sin(θ2) The Attempt at a Solution I was thinking that it would not matter what medium the lens was in, as light would still hit the lens the...

Homework Statement Was wondering if someone could help... Homework Equations 1/f = 1/u + 1/v m = v/u The Attempt at a Solution Using: 1/f = 1/u + 1/v 1/50 = 1/8000 + 1/(v) v = 50.3 mm Then to calculate the linear magnification of the image, using m = v/u with same v and u...

If I have three lenses, each one 50 mm in diameter and with focal lengths of 500mm, -125mm and 150 mm, What would be the EFL if I combined them all together (assuming zero distance between them). I have been looking online for focal lengths of three lens systems but cannot find anything...

Homework Statement A simple camera has a converging lens and the image is in focus on the screen. The paths of three rays from the tree to the lens are shown in the attached diagram. Complete these paths to show the formation of the image on the film.Homework Equations The Attempt at a...

Homework Statement A simple camera has a converging lens of focal length 50.0 mm. It is used to photograph a tree 3.00 m high. The tree is 8.00 m away from the lens. Calculate the distance v between the lens and the film, giving your answer in mm to three significant figures...

Hello, I wanted to ask, is it possible for a magnetic lens to have many focal points, when the magnetic field of the lens is sufficiently large? if so what is the reason for this? how does this give better resolution of images compared to a simple optical lens. I know for a normal optical lens...

The homework problem is "An object 26.0 cm in front of a certain lens is imaged 1.60 cm in front of that lens (on the same side as the object). What is the focal length (in centimeters) of this lens" 1/f = 1/di + 1/do I tried solving based on having distance of object (do) and...

The problem reads "What is the focal length (in meters) of a -4.2 diopter lens" The formula equation I have is = 1/f to get the diopter power -4.2 = 1/f and solve for f I get -.2381 This is a homework problem where the solutions are entered on line. I entered the solution above...

What is the focal length of a thin, flat piece of glass with no curvature? I found that the power is 0 diopters, but I don't know what the focal length is.

Homework Statement An object is located 26.0cm from a certain lens. The lens forms a real image that is twice as high as the object. (i) What is the focal length of this lens? (ii) Now replace the lens used in Part 1 with another lens. The new lens is a diverging lens whose focal...

Homework Statement Diverging lens with focus of 2 meters. The object is 3.66 meters away from the lens. Find the exact image location. Homework Equations 1/object + 1/image = 1/f The Attempt at a Solution I plugged in the numbers with a negative value for the focal length but I...

I have a fisheye lens which sees 180 degrees of the sky. It registers the entire sky on a 640x480 grid of pixels. Let's assume I know where the zenith and north are on the plate. That allows me to find the alt/az of every pixel in the circular image. The fisheye is linear in the distance from...

Homework Statement When using the lens formula: 1/f = 1/u + 1/v for someone who has short sightedness and cannot focus on objects on objects more than 2.5m away, I get: 1/f = 1/infinity + 1/-2.5 f = -2.5 mIf using the formula for someone who had long sightedness and could not focus on...

I got a Zhumell Z8 Dobsonian. The stock lens is decent, I think. One is a 68 degree Plossl and the other is a zoomed in Plossl that I don't know as much about. I want a new lens so I can get better views. I am mostly interested in deep sky objects, seeing as there are only a handful of...

Homework Statement Determine the focal length of a plano-concave lens (n=1.5) which has a radius of curvature of 10 cm. What is its power in diopters? Homework Equations None given. The Attempt at a Solution 1/f=(n-1)(1/R_1-1/R_2)=(1/2)(-0.1)=-1/20. Thus f=5 cm and P=-20 m^(-1)...

Homework Statement A bi-concave lens (n=1.5) has radii of 20 cm and 10cm and a thickness of 5 cm. Describe the image of an object of 2.5 cm of hight and situated at 8 cm from the first side of the lens. Attempt: \frac{1}{f}=(n-1) \left [ \frac{1}{R_1}-\frac{1}{R_2} +...

Homework Statement The focal length of the diverging lens is 74 cm. If an object with height h = 0.6 cm is located at d = 37 cm, what is the height of the image? Homework Equations Thin-Lens Equation: (1/do)+(1/di)=1/f Magnification Equation: m=-di/do The Attempt at a...

Homework Statement Show that the minimum distance between 2 conjugate points (real object and image) for a positive thin lens is 4f.Homework Equations \frac{1}{f}=\frac{1}{S_o}+\frac{1}{S_i}.The Attempt at a Solution I assumed the lens to be biconvex (though I know that I can't. There are so...

What considerations would a lens maker need to take into account when designing a lens? So on top of the chromatic aberrations, glass type and focal length, I have: Lens Thickness Magnification Resolving Power Radius of Curvature Shape(ie cylindrical, spherical, plane) Type(ie convex...

Homework Statement Starting with a real object, which of the following statements are TRUE about the image formed by a single lens? (Choose ALL correct answers, e.g. B, AC, CDF.) A) For a converging lens an object has to be placed between the focal length and the lens in order to form a...

Homework Statement A middle-aged man starts to wear eyeglasses with lenses of 2.0 D that allow him to read a book held as close as 25 cm. Several years later, he finds that he must hold a book no closer than 35 cm to read it clearly with the same glasses, so he gets new glasses. What is the...

Homework Statement A digital camera has a 3x zoom lens whose focal length can be varied between 6-18mm. The lens is assumed to be thin. The image is formed on a CCD sensor whose diameter is 10mm. 1. How large an object can be captured with the camera if the object is at distance of 10m from...

Homework Statement A camper is trying to start a fire by focusing sunlight onto a piece of paper. The diameter of the sun is 1.39e9 m, and its mean distance from the Earth is 1.50e11 m. The camper is using a converging lens whose focal length is 10.8 cm. (a) What is the area of the sun's...

Hi guys, I have a very simple question that arises in a photo forum in Brazil. Some guy put a formula to calculate the maximum resolution possible in a camera lens based on their aperture. The formula is 1800/N = (maximum resolution in lpmm) Were 1800 é a constant and N is the F stop of the...

An object 5 cm tall is 10 cm from a convace lens. The resulting image is one fifth as large as the object. What is the focal length of the lens? I have been doing questions involving focal lenght, but not when the resulting image is a fraction of the original image. i do not know where to...

I'd like to ask does thinner convex lens give a shorter focal length? If so, why is it? thanks very much~~

Hello. I've been struggling with this problem for some time, and honestly I do not know how to solve it. Homework Statement Two positive lenses are to be used as a laser beam expander. An axial 1.0 mm diameter beam enters the short focal length positive lens, which is followed by a...

1. Your task in physics laboratory is to make a microscope from two lenses. One lens has a focal length of 2.8 cm, the other 1.1 cm. You plan to use the more powerful lens as the objective, and you want the eyepiece to be 15 cm from the objective. What is the magnification of your...

Question: Is it possible for a given lens to act as converging lens in one medium and a diverging lens in another? What i was thinking: Yes. Let say we put the lens underwater. It slows the light down and turns the image upside down as it passes through the converging lens, turning it...

Homework Statement I have a concave lens where f < do < R. I have to provide a ray tracing diagram. The Attempt at a Solution I drew the focal ray through the focus and parallel to the principal axis. I drew the principal ray parallel to the principal axis then through the focus. I...

Hi, in questions involving lenses, when using the "thin lens formulae" if my di is negative doesn't that mean the image is on the other side of the lens? in this example however it doesn't seem this holds true.. A doctor examines a patient's skin lesion with a 15 cm focal length...