If Dion is inside a train traveling through a tunnel and stands between two train carriages looking at the side mirror of the leading carriage, what will Dion see in the reflection when the train is halfway through the tunnel?

Provide a very brief response.
Dion will see the tunnel wall in the side mirror's reflection. Since the train is inside the tunnel, the mirror would not reflect the outside landscape or sky. Instead, it will reflect the interior wall of the tunnel that is lit by the train's lights or any existing tunnel lighting. The view will likely be limited to the rough surface of the tunnel's side wall, possibly the tracks below if the mirror is angled downwards, or potentially the reflection of other parts of the train if the mirror angle includes them. Dion's view will be constrained by the position and angle of the mirror and the light availability inside the tunnel.