Experiment with the laser beam direction until no light emerges at. To find the focal length of a concave lens using a convex lens. Two convex lenses of different focal length and an optical bench with four uprights. In this experiment, we will be dealing only with thin lenses. Determines the focal length of a convex lens, when the object distance and image distance focal length of convex lens download. Ncert class 10 science lab manual image formation by a.
As per new cartesian sign convention, focal length of a concave lens is negative and the focal length of a convex lens is positive. Measure the approximate focal length of the lens by focusing a distant object onto a screen and measuring the distance from the lens to the screen using the metre stick. The object will now be situated in the focal plane of the lens, i. You can calculate the focal length of the concave lens using the formula f 2 f 1 ff 1f. A convex lens, convex lens stand, a small screen hard sheet of white papercardboard fixed to a stand, a measuring scale procedure. For a thin double convex lens,refractionacts to focus all parallel rays to a point referred to as the principal focal point.
Focal length of convex lensb11 lab report objectives of the experiment. 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. There are two methods to find the focal length of a concave lens. The thinlens equation is an approximation, do not be disturbed if your results differ from those predicted by equation 12. Ncert class 10 science focal length of concave mirror and. Measure the approximate focal length of the mirror by focusing a distance object onto a screen and. Class 12 physics practical to find the focal length of. What you are considering is specific intensity, which is also called brightnessand it is the energy per second per area per incident solid angle. A transparent material bound by two surfaces, of which one or both surfaces are spherical, forms a lens. Lens focal lenght thin report by fildia putri 12,191 views. You can verify your result by clicking on the show result button. Also, magnification is more for convex lenses having shorter focal length. To determine the rough focal length of the lens, measure the distance between the lens and the screen.
Experiments to measure the focal length of a converging lens. 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. Practical5 focal length of a convex lens by plane mirror method aim. However, if one of the surfaces is flat and the other convex, then it is called a planoconvex lens. A thin convex lens can be characterized by its focal length f, the. Move the paper until you get a sharp image of the world outside the windows, or a distant object such as a tree. After completing experiment 10, i had a broader insight into how converging and diverging lenses worked and their abilities to transform my perspective of an image i. Determining focal lengths of concave and convex lenses.
Experiment to determine the focal distance and magnification. If the object is placed very far away from the lens d o. Converging lenses are convex lenses that converge to the central axis. 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. To verify the expression for the focal length of a combination of two lenses. Therefore, for reading small letters, a convex lens of focal length 5 cm will be preferred. Shine the rays straight into the convex lens see figure. Millions of thanks from depths of my heart to every subscriber and visitor. Find the distance between the optical centre of the lens and the screen. Diverging lens to determine the focal length of a diverging lens, the lens must create a measurable, real image as in part 1.
Convex lenses in this experiment produces inverted. Convex lens converges all the rays and the distance between lens and focus is 40 cm. An optical lens is generally made up of two spherical surfaces. Feb 26, 2016 the percent deviation of focal length in convex lens 1 is 2. Move the lens toward the screen and adjust its position one again a. To determine the focal length of a convex lens by obtaining an image of a distant object apparatusmaterial required. Spread the loveyou can also get class xii practicals on biology, physics, and physical education. Determination of focal length of convex lens using uv method.
Objective to measure the focal length of convex positive or convergent lenses and concave negative or divergent lenses. This allows us to determine the focal length of a convex lens. Record the position of the plane mirror, convex lens and the object pin. Arrange the plane mirror, convex lens and object pin. These two variables are related to the focal length, f, by the lens equation. Practical5 focal length of a convex lens by plane mirror. It will give a virtual upright image if the object is within the focal length. Place the light source in raybox mode on a white sheet of paper. In other words, if the righthand side of the equation is larger, the focal length is smaller. 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. 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. Dec 20, 2015 to find the valueof v for differentvaluesof u in case of a concave mirror and to find the focal length.
When a converging lens is placed between an illuminated object and a screen, there are two positions of the lens for which a sharp image will be formed on the screen. Determination of focal length of convex lens u method. Class 12 physics practical to find the focal length of convex lens. Place the lens on the holder with fixed upright such that the upright is kept at 50 cm mark. 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. 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.
Concave and convex lens powerpoints free pdf ebook. To accomplish this, a real image from a converging lens will. And this right here you can view as the focus of the lens. Physics 2 lab report 7 focal length of lenses focal. Keep the distance between the plane mirror and convex lens as 30cm, 40cm for other set of the readings 4. Repeat the experiment by placing the combination of lenses at different distances away from the wire gauze. Use the lensmakers equation to determine the focal length of a thin lens. To find the focal lengthof a convex lensby plotting graphsbetween u and v or between 1u and 1v. For a converging lens, the focal length is always positive, for a diverging lens it is always negative. Convex lens, optical bench, light source, target image slide, lens mounts. Theory when parallel light rays pass through a thin lens, they emerge either converging or diverging. These type of lenses can converge a beam of light coming from outside and focus it to a point on the other side. This point is known as the focus and the distance between the centre of. However, light cannot be focused through a diverging lens to form a real image unless that light was already converging.
Convex lens uses, examples, definition, ray diagram, formula. Focal length of a convex lens practical experiment c. The focal length of the lens is the distance from the center of the lens to the focal point. Practical5 focal length of a convex lens by plane mirror method. To find the focal lengthof a convex mirror, using a convex lens.
Determine the focal length of a concave lens by combining it with a suitable convex lens. An optical bench with three upright central upright fixed, two outer uprights with lateral movements, a convex lens with lens holder. Introducing a concave lens results in the incoming rays from the convex lens being refracted as shown in the diagram above. Image distance, object distance, image height, object height possible errors are either inaccuracies in the measurements, or that the object or image distance is comparable to the lens thickness the lens should be much thinner than either distance for the calculations to work out simply. Theyre essentially all being focused on that point. 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. Homework statement my task was to determine the focal distance and the magnification of a converging lens. The problem that i have is that when i am calculating the magnification in two differents ways i. Dec 21, 20 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 focus lens obtained. We can conclude the focal length of the convex lens which are. Experiments to measure the focal length of a converging lens the position of the lens holder is adjusted until a sharp image of the object is formed on the screen alongside the object itself.
To determine the focal length of converging lens and its radius of curvature. Determination of focal length of concave lens using convex. Theory and examples class 12 physics practical to find the focal length of convex lens. Determination of the focal length of a convex lens uv method. To find the focal length of a convex lens by plotting graph between u and v. Finding the focal length of a lens using the ray box.
To find the value of v for different values of u in case of a concave mirror and to find the focal length. The focal length of convex lens f 1 is shown inside the simulator window. Fix the convex lens in the middle of the optical bench and place one pin on either side of it. Convex lens is a transparent curved device that is used to refract light. Note that in step 2, the rays leaving the lens are diverging and they will not cross. Measuring the focal length of a converging lens in this experiment, you will measure a series of object distances and corresponding image distances for a converging lens and calculate its focal length. The mean of focal length of both the faces is the focal length f1 of one lens.
It may be of biconvex, plano convex or concavo convex meniscus. Optical bench, plane mirror, object pin, meter scale and holders procedure. The focal length converging lens displacement method purpose. A convex lens gives a real, inverted image if the object is outside the focal length of the lens. Determination of focal length of convex lens u method study. In this experiment, we have chosen two methods to find out the focal length of a spherical lens. Using the proper sign convention, u is negative, u negative, v and f are positive. Describe the shapes of three typical converging positive thin lenses and three typical diverging. Determination of focal length using graphical methods. Focal length of a convex lens practical experiment youtube. Properties of the formed images by convex lens and concave lens.
You will do this by constructing a graph of 1 q vs 1 p and using eq. To determine resistance of a galvanometer by halfdeflection method and to find its figure of merit. The distance between the convex lens and the image, measured roughly with a meter rule would give the approximate focal length of the lens. 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. 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. Engage your students during remote learning with video readalouds.
Check that the convex lens in contact with the given concave lens forms an enlarged image of a nearby object. Teacher packs in experimental science phy pack 5 finding the. And think about how they transmit or refract light. To find the focal length of a convex lens by plotting graphs between u and v or between 1u and 1v. 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. 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. Jan 17, 2020 a the device x is a convex lens of focal length 20 cm.
Theory a lens is a transparent object with two refracting surfaces whose central axes coincide. The relationship between the focal length of the lens and these positions is given by. This will be equal to the rough focal length of the mirror. Repeat the experiment a few times by changing the positions of the convex lens stand and note the corresponding changed position of the screen. If the object is not very far away from the lens, the lens equation must be used to calculate the focal length. Convex lens, optical bench, objects and image pins, meter rule. A convex lens gives a magnified image of an object when it is placed between the radius of curvature and focal length. To find the focal length of a convex mirror using a convex lens. Ncert class 10 science lab manual image formation by a convex lens practical. A thin convex lens can be characterized by its focal length f, the object distance, d o and the image distance, d i. Lenses finding the focal length of a convex lens hold the lens up to the window and hold a piece of paper behind it on the other side of the lens from the window. The relation between the object distance u and the image distance v for a convex lens placed in air is.
Equipment materials ray box with illuminated object, white screen, lens holder, metre rule and lens background the purpose of the experiment is to study image formation by a thin lens. Physics stack exchange is a question and answer site for active researchers, academics and students of physics. To investigate the image formed by a certain thin convex lens. With our light source device and two different lenses on a measureable bench, we could identify the distance between the object and the lens. To find the focal lengthof a concave lens, using a convex lens. Or you can view this length from the lens to that point as the focal length. If it makes a diminished image, change the convex lens with another one of shorter focal length. The focal length of other face can be determined by the turning the nodal slide through 180 and repeating the experiment. Conclusions and discussion after completing experiment 10. If those surfaces are bent outwards, the lens is called a biconvex lens or simply convex lens. By measuring a series of object distanceimage distance pairs, you will be able to experimentally determine the focal length of the convex lens.
They all converge at this point on the other side of the lens. The image in one position will be larger than the other. Place the lens between then and near to the object. Convex and concave lenses purpose in this experiment, you will explore the difference between convex and concave lenses and determine their focal lengths. Determines the focal length of a convex lens, when the object distance and image distance. Intensity is the amount of energy per unit area per unit time. The focal length converging lens displacement method. Feel the different shapes and relate the shapes to the effect of the lens. Ncert cbse solutions for class 10 science chapter 10. In this experiment, the focal length of each lens will be determined using the following three methods.
In particular we will find the focal length of a lens converging using the lens equation. Experiment 1 measuring the focal length of a convex lens parallax method experiment 2 investigating the relationship between the image and object distance for a convex lens. To determine the focal length of a lens using the ray box. This distance is equal to the focal length of the convex lens.
For the rays shown in figures 12, light is assumed to be coming from the left, and going toward the right. Experiment 4finding the position of a virtual image. How does the brightness of the image formed using a convex. Measure the focal length from the center of the convex lens to the focal point. The lens should be placed in such a way that its surface is vertical and perpendicular to the length of the optical bench. Diverging lenses are concave lenses where the rays diverge. 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.
Convex lens the convex lens is a converging lens as it collects the refracted rays, the point of collection of the parallel rays produced from the sun or any distant object. The converging lens is thicker at its center than at its edge. The percent deviation of focal length in convex lens 1 is 2. The relation between u, v and for a convex lens is. The end lam ka yue kenneth 6s 20 date of experiment. Focal length of concave lens experiment study page.
To find the focal length f of a convex lens by plotting graph between 1u and 1v. 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. 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. The distance between the convex lens and object pin is the focal length of the convex lens. To find the focal length of a convex lens by the plane mirror method. The distance from the lens to that point is the principal focal length f 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. Follow steps 2 to 4 of experiment 2 to set the object needle. Just what are the 4 distances involved in your experiments. 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. 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. So remember, concave means it opens inward, like a cave. Adjust the position of the lens until magntief image is sharply focus on the screen. The relationship between u and v and the focal length f for a convex lens is given by.