1. **State the problem:** We are given the function $f(x) = \sqrt{x}$ and asked to determine the reflection represented by the function $f(y) = \sqrt{-x}$. 2. **Recall the reflection rules:** - Reflecting a graph about the y-axis changes $x$ to $-x$ in the function. - Reflecting about the x-axis changes $y$ to $-y$. - Reflecting about the origin changes both $x$ to $-x$ and $y$ to $-y$. 3. **Analyze the transformation:** The function $f(y) = \sqrt{-x}$ replaces $x$ with $-x$ inside the square root. This means the graph of $f(x) = \sqrt{x}$ is reflected about the y-axis. 4. **Conclusion:** The graph of $f(y) = \sqrt{-x}$ is the reflection of $f(x) = \sqrt{x}$ about the y-axis.