13(a)]
where ˆp  is the unit vector along the dipole axis (from –q to q) Also
E
p
+
=
−
q
rq
a
4
0
2
π ε (
)
�
[1 13(b)]
Rationalised 2023-24
24
Physics
The total field at P is
E
E
E
p
=
+
=
−
−
+




+
−
q
q
q
r
a
r
a
4
1
1
0
2
2
π ε
(
)
(
)
�
    =
−
q
a r
r
a
o
4
4
2
2 2
π ε
(
)
�p
(1 14)
For r >> a
E
p
=
44
0
q a3
πεr
ˆ                (r >> a)
(1