Penrose Unilluminable Room Is Impossible To Light

Summary by Krater

Steve Mould explores Penrose's unilluminable room, demonstrating why certain shapes with mirrored walls cannot be fully illuminated by a point source of light, and traces the origin of the puzzle to a 1958 issue of New Scientist magazine.

From the video

Answers: Can a mirrored room always be fully illuminated by a single point source of light?

• Penrose unilluminable room
• Reflection of light in mirrored rooms
• Ellipses and focal points in optics
• Billiard table geometry and reflections
• Particle simulations of unilluminable rooms

What it concludes

• A mirrored room with specific curved boundaries like Penrose's unilluminable room can never be fully illuminated by a single point source of light, as certain regions will always remain in darkness due to the properties of ellipse focal points and reflections.
• Ray light originating from one focal point of an ellipse will always reflect onto the other focal point, which explains why certain shapes restrict light pathways.
• Any ray of light passing between two focal points of an ellipse will never end up outside of those two focal points upon reflection.