Problem 3.41

A point electric dipole with a moment $\mathbf{p}$ is placed in the external uniform electric field whose strength equals $\mathbf{E}_ {0}$. with $\mathbf{p} \uparrow \uparrow \mathbf{E}_ {0} .$ In this case one of the equipotential surfaces enclosing the dipole forms a sphere. Find the radius of this sphere.