TITLE: THE FOCAL LENGTH OF A LENS AIMS: The aims of this experiment are to: (a) determine the focal length of a convergi

[answerhappygod]

Title The Focal Length Of A Lens Aims The Aims Of This Experiment Are To A Determine The Focal Length Of A Convergi 1 (73.78 KiB) Viewed 24 times

TITLE: THE FOCAL LENGTH OF A LENS AIMS: The aims of this experiment are to: (a) determine the focal length of a converging lens; (b) compare several graphical methods of analyzing data. Theory The object distance, image distance and focal length of a thin lens are related by the equation: 111 JUV (A.I.1) f is the focal length, - the distance from the lens to the point at which a parallel incident beam of light is focused. It is a constant for a given lens, In our sign convention the focal length is positive for a converging lens, such as the one used in this experiment. u is the object distance - the distance from the lens to the object. v is the image distance - the distance from the lens to the image. Jens screen object image The sign convention we use is that distances to real objects and images are positive, and those to virtual objects and images are negative. Real objects are those such that the light from them is diverging when it strikes the lens. In this experiment only real objects will be used. Real images are those formed by light which is converging when it leaves the lens. Only real images can be cast onto a screen, and so you will deal only with real images in this experiment.
1) Fix the distance u and move the screen until a sharp image of the grid is produced on the screen. Make sure that v>u. Measure the values of u and v and record them in the table below. 2) Produce a second set of readings without taking another set of measurements by interchanging your values of u and v. This is possible because of the symmetry of equation (A1.1). 3) Repeat steps 1) and 2) for at least four more object positions. Your values of u should cover as large a range as possible, with y > u for each set. RESULTS: The following data were obtained; U (cm) V (cm) 100 23.5 25 85 26.5 70 29.5 55 37.5 40 40 37.5 29.5 55 70 85 26.5 25 23.5 100
I V IV u+v +! 11 V u V Mean Analysis (1) Plot u against y. This gives a hyperbola. Draw on your graph the line u = v. At the intersection of this line with the experimental curve u = v = 25. Explain why this is so You need not show the origin on your graph, but you must use the same scale for both axes. N.B. You must plot this graph first, so that you can choose suitable axes for graph (ii). From the graph.fr (ii) Plot - against This should give a straight line of slope - 1 and intercept 1/f on each axis.
Explain why this is so. This time you must show the origin in order to obtain both intercepts, and you must use the same scale on both axes. Use the value you obtained for f from graph (i) to ensure that your axes extend far enough for you to be able to read off both intercepts. A1,3 From the graph, and f Mean and so f = f (iii) Plot uy against u + v The resulting graph should be a straight line of slope f passing through the origin. Explain why this is so. In this case the readings you obtained by interchanging values of u and v do not give additional points. When plotting the graph you must show the origin and ensure that your line passes through the origin. From the graph f (iv) Calculate f directly from your values of 1 1 - + 11 V 1 From table: mean Hencef
Conclusions Your four values off should be reasonably similar. Are they? Mean value of ſobtained = Explain which graph(s) should give the most accurate value of f.