School geometry: Golfing exercise

I have the following exercise to solve:

A (golf) player hits the ball at B, the ball touches line a exactly once and goes into the whole L. How does the ball's way look like?

My idea has been the following (and I have forgotten most of my basic school geometry): The incoming angle of the ball must be equal to the outgoing one, hence I was just dividing the distance from B to L to determine where the ball must hit a. But somehow it feels that I am missing something, but I don't know what...any help appreciated.

draw $L'$, reflection of $L$ across $a$, and join $B$ with $L'$.
To see why that works, see the diagram below: right triangles $ALH$ and $AL'H$ are congruent (SAS), whence $\angle LAH \cong \angle L'AH$. On the other hand we have $\angle L'AH \cong \angle BAa$ for they are vertical angles. It follows that $\angle LAH \cong \angle BAa$, as required.