Step 1: Simplify the given expression for \( n \).
We are given that \( n = \sqrt{\frac{16}{81}} \), so:
\[
n = \frac{4}{9}
\]
Step 2: Find the square root of \( n \).
The square root of \( n \) is:
\[
\sqrt{n} = \sqrt{\frac{4}{9}} = \frac{2}{3}
\]
\[
\boxed{\frac{4}{9}}
\]