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