A concave lens is thinner at the center that at the edges. If those surfaces are bent outwards, the lens is called a biconvex lens or simply convex lens. Describe the shapes of three typical converging positive thin lenses and three typical diverging. Determination of focal length of a convex lens experiment edunovus online smart. Diverging lens to determine the focal length of a diverging lens, the lens must create a measurable, real image as in part 1. Recall from a previous lab that the main property of a lens is its focal length. 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 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. Jan 17, 2020 ncert class 10 science lab manual focal length of concave mirror and convex lens.
So the more highly curved the surface, the shorter is. In this experiment, we have chosen two methods to find out the focal length of a spherical lens. Determines the focal length of a convex lens, when the object distance and image distance. To find the focal length of a concave lens using a convex lens by. The bouncing back of light on hitting any mediumsurface is called reflection of light. Optical bench, light box, lenses, lens holders, illu minated target object, white screen with scale, mirror. To determine the focal length of a lens using the ray box. The thin lens equation is an approximation, do not be disturbed if your results differ from those predicted by equation 12. The lens itself can have a positive focal length, in which case it brings parallel light rays together at a common point, or a negative focal length, which causes parallel light rays to appear to diverge from a common point. The task of providing the same conditions of intensity profile transformation for a broad spectral bandwidth can be solved by refractive beam shaping optics with achromatic design. A thin convex lens can be characterized by its focal length f, the object distance, d o. Focal length of convex lens report inappropriate project. Practical5 focal length of a convex lens by plane mirror method.
To determine the focal length of converging lens and its radius of curvature. Determination of focal length of concave mirror and convex lens. 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. Move the paper until you get a sharp image of the world outside the windows, or a distant object such as a tree. Principle two experimental variants for the determination of the focal length of a convex lens are suggested, so that at least once the students can discuss the. If r1 r2,then you will find the thickness of lens 1 will be more than lens 2. Determining the focal length of a converging lens physicslab. Focal length of lenses march 24, 2009 when an object is placed at a distance p from a convex lens with focal length f, then if p f, a real image is formed at some distance i away from the lens see the figure below. 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 this experiment the focal length of a lens is found out. To determine the focal length of a spherical convex lens by lens formula method by lens replacement method. Experiments to measure the focal length of a converging lens. Place the object o at one end of meter scale and the image screen. 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.
View lab report physics 2 lab report 7 focal length of lenses from physics 2 at howard university. The purpose of this experiment is to determine the focal length of a thin converging lens. Finding the focal length of a convex lens by plotting graph. Converging lens image and object relationships crossed arrow target viewing screen lens d i d o s o s i f figure 7. To find the focal length of a convex lens by plotting graphs between u and v or. Ncert class 10 science lab manual focal length of concave. Thin lenses and optical instruments equipment 1 meter optical bench with 5 moveable mounts, lighted test object, 3 lens holders, screen, 2 short focal length double convex lenses l1, e1, 2 medium focal length double convex lenses l2 and l3, 1 long focal length double convex lens l4, 1 double concave lens l5.
Focal length of convex lensb11 lab report objectives of the experiment. The relationship between u and v and the focal length f for a convex lens is given by. Theory when parallel light rays pass through a thin lens, they emerge either converging or diverging. For the rays shown in figures 12, light is assumed to be coming from the left, and going toward the right. To find the focal length of a convex lens by plotting graph between u and v.
Pdf a sensitive thresholding method for confocal laser. The problem that i have is that when i am calculating the magnification in two differents ways i. Convex lens, optical bench, light source, target image slide, lens mounts, and screen. Optics track, light source, view screen, ruler, and a convex and concave lens. Finding the focal length of a given convex lens papers. Practical5 focal length of a convex lens by plane mirror method aim. If the focal length of a double convex lens is 20cm, then. 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 determine the focal length of a convex lens by obtaining. Introducing a concave lens results in the incoming rays from the convex lens being refracted as shown in the diagram above. Use the lensmakers equation to determine the focal length of a thin lens. It is the point where the image comes into focus when seen though the lens. 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 the focal length of a convex lens by obtaining an image of a distant object apparatusmaterial required. 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. Note that in step 2, the rays leaving the lens are diverging and they will not cross. Physics 2 lab report 7 focal length of lenses focal. Finding the focal length of a convex lens by plotting. Feb 26, 2016 the percent deviation of focal length in convex lens 1 is 2. The focal lens of a lens is the distance from the principal focus to the optical centre. 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. 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. Pdf achromatic refractive beam shaping optics for broad. 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. To find out the focal length of a convex lens youtube. Calculate the focal length of the convex lens by using the formula given.
So the light beams passing through the lens are spread out or diverged. Therefore, the concave lens is called a diverging lens. Convex and concave lenses purpose in this experiment, you will explore the difference between convex and concave lenses and determine their focal lengths. Measurement of the focal length of a converging lens. In particular we will find the focal length of a lens converging using the lens equation. Furthermore, during the convex lens experiment in test 1, the participants found that the. Focal length is the distance between optical centre of lens. Convex lens uses, examples, definition, ray diagram, formula. Optical bench, plane mirror, object pin, meter scale and holders. 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. The focal length converging lens displacement method purpose.
Determination of focal length of a convex lens experiment. To find the focal length of a convex lens by the plane mirror method. Aim the experiment is to enable students to physically observe the image produced by 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. Determining focal lengths of concave and convex lenses. Two converging achromatic lenses with focal lengths of about 6 cm and cm. 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. By measuring a series of object distanceimage distance pairs, you will be able to experimentally determine the focal length of the convex lens. Focal length of concave lens experiment study page.
Determines the focal length of a convex lens, when the object distance and image distance focal length of convex lens download. The focal length of a lens depends on the curvature of each surface. Repeat the measurement by adjusting the distance between lamphousing and the screen s to roughly about 5. Before getting started with the experiment, it is important to understand a few. 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. In this experiment, we will be dealing only with thin lenses. Jul, 2008 homework statement my task was to determine the focal distance and the magnification of a converging lens.
Jan 18, 2018 focal length of a convex lens class 12th duration. To investigate the image formed by a certain thin convex lens and to determine its focal length. A convex lens, convex lens stand, a small screen hard sheet of white papercardboard fixed to a stand, a measuring scale. Physics practical class 10 introduction light shows the property of reflection and refraction. Determine the focal length of a concave lens by combining it with a suitable convex lens. These type of lenses can converge a beam of light coming from outside and focus it to a point on the other side. The focal length converging lens displacement method. To accomplish this, a real image from a converging lens will.
Either kind of lens can form real or virtual images from real or virtual objects. Finding the focal length of a lens using the ray box. To determine the focal length of the convex lens check out more video on. Experiment with the laser beam direction until no light emerges at. Teacher packs in experimental science phy pack 5 finding the.
Measure the focal length from the center of the convex lens to the focal point. Investigate the relationship between power and focal length. 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. Let me start with a simple explanation keeping the centre of curvature c same,draw two lens with r1 and r2 as the respective raduis of curvature. To measure and compare the focal lengths of some lenses using different methods, and to determine the magnification of a simple telescope. However, light cannot be focused through a diverging lens to form a real image unless that light was already converging. 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. In this lab, the student will determine the focal length of a given lens by using an optical bench to make measurements of object and image distances.
Experiment to determine the focal distance and magnification. Jul 27, 2012 to find out the focal length of a convex lens. What is the relationship between the thickness of a lens and. 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. Convex lens, optical bench, objects and image pins, meter rule.
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