If P be the dipole moment and E be the electric field then the potential energy of a dipole is given by: W= P.E. \\cos \ heta Now, given: P.E. \\cos {60}^{o} = 2 \ imes {10}^{-19}\\ J Then, P.E= 4 \ imes {10}^{-19}\\ J Now, the work done to move the dipole further by {30}^{o} , W = P.E. \\cos {90}^{o} - P.E. \\cos {60}^{o} =0 - (4 \ imes {10}^{-19} \ imes \\frac{1}{2})\\ J or, |W|=2 \ imes {10}^{-19}\\ J