to find the focal length of a convex lens by plotting graph between u and v or between 1/u and 1/v
Answers
Answer:
Observations
Rough focal length of the given convex lens = …….cm
Actual length of the knitting needle x=…….cm
Observed distance between the object needle and the lens
when knitting needle is placed between them y =…….cm
Observed distance between the image needle and the
lens when knitting needle is placed between them z =…….cm
Index correction for the object distance
Calculations
Calculations of focal length by graphical methods:
(i) u-v Graph. Select a suitable but the same scale to represent u along X’-axis and v along Y-axis. According to sign conventions, in this case, u is negative and v is positive. Plot the various points for different sets of values of u and v from observation table second quadrant. The graph comes out to be a rectangular hyperbola as shown in graph between u and v.
Draw a line OA making an angle of 45° with either axis (i.e., bisecting ∠YOX’) and meeting the curve at point A. Draw AB and AC perpendicular on X’- and Y-axes, respectively.
The values of u and v will be same for point A. So the coordinates of point A must
to-find-the-focal-length-of-a-convex-lens-by-plotting-graphs-between-u-and-v-or-between-1u-and-1v-3
