t
i
m
e
0
.
f
o
r
w
a
r
d
w
a
v
e
a
m
p
l
i
t
u
d
e
1
.
b
a
c
k
w
a
r
d
w
a
v
e
a
m
p
l
i
t
u
d
e
0
.
5