$E_1$ and $E_2$ are magnitudes of electric field due to a dipole, consisting of charges $-q$ and $+q$ separated by distance $2a$, at points $r (>> a)$ (1) on its axis, and (2) on equatorial plane, respectively. Then $\left(\frac{E_1}{E_2}\right)$ is : (A) $\frac{1}{4}$ (B) $\frac{1}{2}$ (C) 2 (D) 4