Ambient (n
o
, k
o
)
Substrate (n
s
k
s
)
Film 1 (n
1
k
1
d
1
)
Film 2 (n
2
k
2
d
2
)
Film i (n
i
k
i
d
i
)
f
r
s
r
p
E
r
E
i
E
P
E
S
