A long straight wire carries a current i. Let B₁ be the magnetic field at a point P at a distance d from the wire. Consider a section of length l of this wire such that the point  P lies on a perpendicular bisector of the section. Let B₂ be the magnetic field at this point due to this section only. Find the value of of d/l so that B₂ differs from B₁ by 1%.