Suppose Ram has placed a ball in front of a concave mirror of focal length (f) at various distances (u) and he has measured the corresponding image distances (v). From the values of u and v, Ram is able to plot a graph of 1/v against 1/u. From the graph, Ram has observed that x intercept and y intercept are 0.1 cm and 0.11 cm, respectively. Then the focal length of the mirror is: