Let the two ends of the object be at distance u_{1}= u – L/2 and u_{2} = u + L/2, respectively, so that |u_{1}–u_{2}|= L. Let the image of the two ends be formed at v_{1} and v_{2}, so that the image length would be

the image of the two ends will

Since the object is short and kept away from focus, we have