Answer
There is a valley at the other end.
Work Step by Step
We can express the length of the nanostructure in terms of $\lambda$:
$L = \frac{1500~nm}{1000~nm} = 1.5~\lambda$
Since the length of the nanostructure has the form $(m+\frac{1}{2}) \lambda$ where $m$ is an integer, there is a valley at the other end.
