Given, charge of dipole, q=500×10−6C Separation between charges, 2a=10‌cm=10×10−2m Distance of location from mid point of axis, r=25‌cm=25×10−2m ∵ Electric field on axis of dipole, E=
4kqar
(r2−a2)2
where, k is Coulomb's constant =9×109C2m−2N−1
E=
4×9×109×500×10−6×5×10−2×25×10−2
[(25×10−2)2−(510−2)2]2
=
2.25×105
[0.0625−0.0025]2
=
2.25×105
(0.06)2
=
2.25×105
36×10−3
=6.25×107≈6×107NC−1 The result is close to option (a).