Draw a graph of V vs. U. V (cm) C A 150 B O U (cm) Draw a line making 450 with the x-axis to cut the graph at A. Draw AB perpendicular to the x- axis. OAB is an isosceles right triangle and therefore, OB = AB = OC. This means that point A corresponds to U = V. At point A, the equation 1/U + 1/V = 1/f becomes: 2/U = 1/f, or U = 2f. This means that the distance OB = 2f. Similarly, OC = 2f. Measure and record OB and OC and record the average of these two measures as 2f. Find the average focal length of the lens and record it as f. Now find the percent difference of focal length obtained from two graphs. [Remember to find percent difference: % difference = (Difference in two values /average) x100%]No of observations Object distance(u) cm Image distance(v) cm Focal length (f) cm 1 200 124 0.005 2 190 128 0.005263 3 180 133 0.005556 4 160 148 0.00625 5 150 156 0.006667 6 140 171 0.007143