Room IV / Refraction
Caustic Clock
Exact local time
The hour turns the left lens. Minutes turn the right lens. Their concentrated light carries the four time digits; seconds pass through it as a shimmer.
Construction
Gold marks the hour lens axis; magenta marks the minute lens axis. Cyan paths are traced rays. The readable focus is the overlap rather than a separate clock face.
How to read it
Read the concentrated light at the center. The moving gold line is the current second traveling through the focus.
What changes
The two glass forms rotate independently, so every hour-minute pair produces a different field of rays.