The lens used above is convex and the focal length is positive. The lens is moved until a sharp image is formed on the screen. If those surfaces are bent outwards, the lens is called a biconvex lens or simply convex lens. In this experiment, we will be dealing only with thin lenses. Aim the experiment is to enable students to physically observe the image produced by the lens. Focal length of concave lens experiment study page. Theory when parallel light rays pass through a thin lens, they emerge either converging or diverging. In this experiment, we have chosen two methods to find out the focal length of a spherical lens. Converging lenses are convex lenses that converge to the central axis. Determination of focal length of a converging lens and mirror. Have done the experiment with title title lens fcal lenght thin. Focal length of a convex lens uv method convex lens or plus lens is a converging lens.
From the results of the lab we calculated the focal length of our converging lens to be 19. Where f is the focal length, u is the distance between the object and. A rayzer lightbox with baseobard, two concave lenses one thick,one thin. Either kind of lens can form real or virtual images from real or virtual objects.
Homework statement my task was to determine the focal distance and the magnification of a converging lens. Diverging lenses are concave lenses where the rays diverge. Convex and concave lenses purpose in this experiment, you will explore the difference between convex and concave lenses and determine their focal lengths. A lens holder, a converging convex lens, an optical bench, a lightbulb socket, a lowwatt light bulb, a rectangular target, a target holder, and a tape measure. We hope this cbse class 10 science lab manual focal length of concave mirror and convex lens helps you in your preparation for cbse class 10 board examination practical exams. We can conclude the focal length of the convex lens which are 9. Light refracts when passing through media with different indices of. View lab report physics 2 lab report 7 focal length of lenses from physics 2 at howard university. For a converging lens for example a convex lens, the focal length is positive, and is the distance at which a beam of collimated light will be focused to a single spot. Convex lens, optical bench, objects and image pins, meter rule. For the rays shown in figures 12, light is assumed to be coming from the left, and going toward the right.
Ray diagram for an object infinitely far away from the lens. The focal length of convex lens f 1 is shown inside the simulator window. Results controlled variables focal length of convex lens. The image formed when the concave and convex lens were not in contact was inverted and reduced and the calculated value of the focal length was 150 mm introduction. For a thin lens in air, the focal length is the distance from the center of the lens to the principal foci or focal points of the lens. To find the focal length of a convex lens by plotting. Focal length of a convex lens practical experiment youtube. Your lab report for this experiment should contain the following sections. Jun 08, 2016 focal length of a convex lens practical experiment c. The objective of this experiment is to measure the focal length of a converging lens and a diverging lens. Dec 21, 20 lens focal lenght thin report by fildia putri 1.
The problem that i have is that when i am calculating the magnification in two differents ways i. The overall aim of this experiment is to demonstrate how focal length and image. Focal length is the distance between optical centre of lens. Jan 18, 2018 focal length of a convex lens class 12th duration. This allows us to determine the focal length of a convex lens. The image formed when the concave and convex lens were not in contact was inverted and reduced and the calculated value of the focal length was. An optical bench with three upright central upright fixed, two outer uprights with lateral movements, a convex lens with lens holder, two optical needle, one thin, one thick a knitting needle and a half meter scale. Measure the approximate focal length of the mirror by focusing a distance object onto a screen and measuring the distance from the mirror to the screen. In particular we will find the focal length of a lens converging using the lens equation. Focal length of convex lensb11 lab report objectives of the experiment. Difference between convex and concave lens with figure.
Determination of focal length of convex lens u method. Determination of the focal length of a convex lens uv method. The distance between the lens and the screen is the focal length of the lens. One characteristic feature of all thin lenses and concave mirrors is the focal length, f, and is defined as the image distance of an object that is positioned infinitely far way. Arrange the plane mirror, convex lens and object pin with help of holder. To measure the focal length of a converging convex lens. A thin convex lens can be characterized by its focal length f, the object distance, d o. To determine the focal length of a spherical convex lens u2666 by u201clens formula methodu201d filename. Physics 215 experiment 14 thin lenses 79 advance reading urone, chapter 24, section 246 objective. Notes on power of lens and measurement of focal length. Theory a lens is a transparent object with two refracting surfaces whose central axes coincide.
First of all, the rough focal length of the given convex lens is measured by focusing a distance object on wall or on a screen. The lens is set up in a suitable holder with a plane mirror behind it so that light passing through the lens is reflected back again fig. Fix the convex lens on the lens holder or stand and place it place it on the table near an open window of the laboratory. Convex lens, optical bench, light source, target image slide, lens mounts, and screen. If two lenses of fecal lengths f 1 and f 2 are kept in contact, the focal length f of the combination is given by.
A converging lens always has two focal points, the primary focal point on the near side of the lens towards the oncoming light rays and a secondary focal point on the far side of the lens away from the oncoming light rays. To find the focal length of a convex lens by the plane mirror method. The thinlens equation is an approximation, do not be disturbed if your results differ from those predicted by equation 12. Rays of light from an object very far away from a thin. You can calculate the focal length of the concave lens using the formula f 2 f 1 ff 1f. Where f is the focal length, u is the distance between the object and the lens v is the distance between the image and the lens. Repeat the experiment by placing the combination of lenses at different distances away from the wire gauze. Practical5 focal length of a convex lens by plane mirror method.
Visualizing a virtual image is possible but dicult. Experiments to measure the focal length of a converging lens. Experiment 3 focal length concave mirror and convex lens. Lens focal lenght thin fildia putri, rafika sri rahayu, nul lailah, nurul wisna afianti, nur rahmah marisa raden. Note that in step 2, the rays leaving the lens are diverging and they will not cross. Practical5 focal length of a convex lens by plane mirror. To find the focal length of a convex lens by plotting graphs between. Experiment 11 to find the focal length of a concave lens using a. Focal length of a convex lens practical experiment c. It will give a virtual upright image if the object is within the focal length. To find the focal length of a convex lens by plotting graphs between u and v and between 1u amd 1v. Practical5 focal length of a convex lens by plane mirror method aim. Pdf on nov 25, 2014, deborah sand and others published lenses find, read. Optical bench, light box, lenses, lens holders, illu minated target object, white screen with scale, mirror.
For any questions pertaining to cbse class 10 science practicals focal length of concave mirror and convex lens material, feel free to leave queries in the comments section. Using the proper sign convention, u is negative, u negative, v and f. Diverging lens to determine the focal length of a diverging lens, the lens must create a measurable, real image as in part 1. Do not change this position during this part of the experiment. Place the lampbox well outside the approximate focal length see notes. Note, parallel rays of light converge at the focus point. We cannot use an optical method to determine the focal length of a convex mirror without using a convex converging lens since a convex mirror does not form a real image of an object in front of it or even parallel rays coming from infinity. The focal length of a thin convex lens can be easily measured by using it to form an image of a distant light source on a screen. The focal length of a convex lens is positive, while that of a concave lens is negative. An extended hemispherical lens is a special type of plano convex lens, in which the lens s curved surface is a full hemisphere and the lens is much thicker than the radius of curvature. Experiment to determine the focal distance and magnification.
Jul, 2008 homework statement my task was to determine the focal distance and the magnification of a converging lens. Feb 26, 2016 the percent deviation of focal length in convex lens 1 is 2. The thin lens equation is an approximation, do not be disturbed if your results differ from those predicted by equation 12. We also touch upon the applications of lenses in daytoday life. After conducting the experiment seven times, and calculated the focal length for each we can. This point is known as the focus and the distance between the centre of the lens to the focus is called the focal length of convex lens. The bouncing back of light on hitting any mediumsurface is called reflection of light. By measuring a series of object distanceimage distance pairs, you will be able to experimentally determine the focal length of the convex lens. The relation between the object distance u and the image distance v for a convex lens placed in air is. Place the lens on the holder with fixed upright such that the upright is kept at 50 cm mark. To determine the focal length of a convex lens by obtaining. Ncert class 10 science lab manual focal length of concave.
Finding the focal length of a convex lens by plotting graph. Converging lens, screen, lampbox with crosswire, metre stick, retort stand. Generally, a convex lens forms a real image, but it can also create a virtual image when the object is in the middle of the focus and optical centre. An important property of a lens is its focal length, f. An extended hemispherical lens is a special type of planoconvex lens, in which the lenss curved surface is a full hemisphere and the lens is much thicker than the radius of curvature. For a converging lens, the focal length is always positive, for a diverging lens it is always negative. In this section of the experiment, we will use two lenses to form a real image of the virtual image from a concave negative focal length lens. In this experiment, the focal length of each lens will be determined using the following three methods. To find the value of v for different values of u in case. Objective to measure the focal length of convex positive or convergent lenses and concave negative or divergent lenses.
The focal lengths of a biconvex lens and a concave mirror are shown in figures 1 and 2, respectively. Introducing a concave lens results in the incoming rays from the convex lens being refracted as shown in the diagram above. To find the focal length f of a convex lens by plotting graph between 1u and 1v. Determine the focal length of a concave lens by combining it with a suitable convex lens. Experiment 3 focal length concave mirror and convex lens q. A thin convex lens can be characterized by its focal length f, the. Place the object o at one end of meter scale and the image screen i at the end so that distance apart is about 90 cm. Convex lens the focal length of a convex lens can be measured by uv method. The focal length converging lens displacement method. To investigate the image formed by a certain thin convex lens and to determine its focal length. How to find the focal length of convex mirror using convex. Dec 08, 2018 the focal length of a convex lens is positive, while that of a concave lens is negative.
Convex lens, optical bench, light source, target image slide, lens mounts. To determine the focal length of a thin lens and to explore the difference between convex and concave lenses and to determine their focal lengths. To find the focal length of a convex lens by plotting graphs between u and v or between 1u and 1v. Determination of focal length of concave lens using convex. Measure the focal length from the center of the convex lens to the focal point. For a thin lens in air, the distance from the lens to the spot is the focal length of the lens, which is commonly represented by f in diagrams and equations. Convex lens uses, examples, definition, ray diagram, formula. Physics practical class 10 introduction light shows the property of reflection and refraction. In this case 1 u is negligible, and the focal length is then given by. To determine the rough focal length of the lens, measure the distance between the lens and the screen. To accomplish this, a real image from a converging lens will. Using the ray box, calculate the focal length f of the convex lens. A convex lens, convex lens stand, a small screen hard sheet of white papercardboard fixed to a stand, a measuring scale.
Investigate the relationship between power and focal length. When a concave lens of focal length f 2 is placed coaxially in contact with a convex lens of focal length f 1 and if f is the focal length of the combination, then, therefore, the focal length of the concave lens, b lens out of contact method. A convex lens is called a converging lens whereas a concave lens is. If the concave lens was not there and the object was at a distance greater that its focal length the convex lens would form a real image. How to find the focal length of convex mirror using convex lens.
Repeat the measurement by adjusting the distance between lamphousing and the screen s to roughly about 5. The focal length converging lens displacement method purpose. Determination of the focal length and the power of a diverging concave lens 5. The relationship between u and v and the focal length f for a convex lens is given by. Finding the focal length of a convex lens by plotting. Conclusion from the results of the lab we calculated the. The distance between the convex lens and the image, measured. The lens should be placed in such a way that its surface is vertical and perpendicular to the length of the optical bench. Experiment 4finding the position of a virtual image. To determine the focal length of a convex lens by obtaining an image of a distant object apparatusmaterial required. Physics 2 lab report 7 focal length of lenses focal. This is to give the student a fair idea as to how the lens equation with the measured quantities can be manipulated to obtain the focal length of the lens and also use the graphical method to determine the focal length of a lens. To find the focal length of a convex lens by plotting graphs between u and v or. Measurement of the focal length of a converging lens.
As per new cartesian sign convention, focal length of a concave lens is negative and the focal length of a convex lens is positive. Purpose of this experiment to determine focal length of a convex lens and a concave lens, graph plots relationship between distance of shadow to distance of objects in order to obtain value of focal distance based on graphs, and compare theoretical values with the results of graph plots distance. Keep the given convex lens of known focal length, f 1, in contact with the concave lens whose focal length to be determined. These type of lenses can converge a beam of light coming from outside and focus it to a point on the other side. If the focal length of a double convex lens is 20cm, then. A convex lens gives a real, inverted image if the object is outside the focal length of the lens. Convex lens screen purpose to determine the focal length of a thin lens and to explore the difference between convex and concave lenses and to determine their focal lengths. To determine resistance per cm of a given wire by plotting a graph for potential difference versus current ohms law. On the contrary, the image formed by the concave lens is erect, virtual and smaller, than the object. Repeat for a variety of object distances, ensuring that it is always greater than the approximate focal length. The percent deviation of focal length in convex lens 1 is 2.
Look at the lenses in front of you and try to distinguish the different. Departement of chemistry, fmipa state university of makassar 20 abstract. Measure the distance between the lens and the screen image distance using the metre stick. To measure and compare the focal lengths of some lenses using different methods, and to determine the magnification of a simple telescope. To determine the focal length of a spherical convex lens by lens formula method by lens replacement method. Teacher packs in experimental science phy pack 5 finding the.
If the object is placed very far away from the lens d o. Calculate the focal length of the convex lens by using the formula given. In other words, if the righthand side of the equation is larger, the focal length is smaller. Finding the focal length of a lens using the ray box. A convex lens, convex lens stand, a small screen hard sheet of white papercardboard fixed to a stand, a measuring scale procedure. Optical bench, plane mirror, object pin, meter scale and holders. Optical bench, plane mirror, object pin, meter scale and holders procedure. Jan 17, 2020 ncert class 10 science lab manual focal length of concave mirror and convex lens. To determine resistance of a galvanometer by halfdeflection method and to find its figure of merit. This experiment deals with 4 different ways of measuring the focal length of a double convex lens. Optical instruments 1 introduction 2 focal length of a.