Halliday, Resnick & Walker — Electric Fields: Problem 36

36 Equations 22-8 and 22-9 are approximations of the magnitude of the electric field of an electric dipole, at points along the dipole axis. Consider a point P on that axis at distance \(z = 6.00d\) from the dipole center (\(d\) is the separation distance between the particles of the dipole). Let \(E_{appr}\) be the magnitude of the field at point P as approximated by Eqs. 22-8 and 22-9. Let \(E_{act}\) be the actual magnitude. What is the ratio \(E_{appr}/E_{act}\)?