ABSTRACT
The last integral is equal to zero since ∂Φ(r)/∂z = (∂Φ(r)/∂r) (r ⋅ n(x, y)) = 0 and because r ⊥ n when z = 0.
Equation (6.21) yields
p(M ) = p0 2pi
∂
∂z
∫∫ S
eikr
r dx dy =
p0
2pi ∂
∂z
dϕ
eikr dr
= –
p0
ik
∂
∂z
[ eikz –
1 2pi
eikr1 (ϕ) dϕ
] = –p0
[ eikz –
z
2pi
r1(ϕ) dϕ ]
.
