An electric dipole of dipole moment `vec(p)` consists of point charges + q and - q separated by a distance 2a apart. Deduce the expression for the electric field `vec(E )` due to the dipole at a distance x from the center of dipole on its axial line in terms of the dipole moment `vec(p)` . Hence show that in the limit `a to 0 vec(E )=(2 vec(p))/((4pi epsilon_(0)x^(3)))`.