Charges –q and +q located at A and B, respectively, constitute an electric dipole. Distance AB = 2a, O is the mid point of the dipole and OP is perpendicular to AB. A charge Q is placed at P where OP = y and y >> 2a. The charge Q experiences an electrostatic force F. If Q is now moved along the equatorial line to P such that
$\mathrm{OP}^{\prime}=\left(\frac{\mathrm{y}}{3}\right)$, the force on Q will be close to : $\left(\frac{\mathrm{y}}{3} \gg 2 \mathrm{a}\right)$