Suppose the lower $z \le 0$ halfspace of $\mathbb{R}^3$ is filled with a rigid close-packing of unit-radius spheres. (I don't think it matters much for my purposes if it is an FCC or an HCP packing.) Shoot in from $z>0$ another sphere/ball $S$ of radius $R$ along a random ray at a random angle $\phi$ (w.r.t. the $xy$-plane). Perhaps $R>1$, maybe even $R \gg 1$; but also perhaps $R<1$.

^{ (Sphere packing image from Ed Pegg Mma Demo.) }

$S$ bounces from the rigid unit-spheres halfspace boundary via elastic collision, perhaps ricochetting from several in the top layer—or near-top layers—before emerging free into the upper halfspace $z>0$.

. Is it true that, as $R \to \infty$, the angle of reflection from the $xy$-plane approaches the angle of incidence $\phi$, despite the (inevitable) ricochetting?Q1

. Is it true that, for $R<1$, the distribution of the angles of reflection, for a random ray at incidence angle $\phi$, approaches a diffuse reflection cone independent of $\phi$?Q2

. Is it true that, for $R \ll 1$, some trajectories would never emerge from the lower halfspace?Q3

For small $R$, one might instead think of lightrays bouncing from mirrored spheres.^{1}

^{1}(Distantly) related: "Light reflecting off Christmas-tree balls".