Prism Light Path

A beam of white light enters a glass prism. Rotate it one degree. The rainbow fans open. Route each colour to its target. Real physics. Every ray computed.

Prism Light Path is an optics puzzle built on Snell's Law. Every beam trajectory is computed from real physics equations running at sixty frames per second.

A white light source emits a beam across a dark optical bench. A glass prism sits in its path. The player rotates the prism. The beam enters the first glass surface, bends toward the normal, crosses the interior, exits the second surface, bends away from the normal — and emerges as a fan of colour. Red bending least, violet bending most, because glass has a slightly different refractive index for every wavelength of light. The game models this using the Cauchy dispersion formula: each of the seven traced wavelengths has its own refractive index, each refracts at its own angle at every surface, and each follows its own path to the far wall.

Three puzzle modes, each introducing a different physical concept.

FOCUS mode traces a single wavelength — pure geometric optics. One beam, one prism, one target. The player learns how a glass surface bends light and how two refractions through a prism combine to produce a net deflection. Rotating the prism one degree shifts where the beam lands. The player who has internalised this relationship — the one who can rotate to a target position without trial and error — has learned refraction.

SPECTRUM mode uses white light and full dispersion. The prism splits the beam into seven components. Three colour-coded targets sit on the far wall: one requiring red light, one green, one violet. The player must rotate the prism so all three wavelength-beams land simultaneously on their matched targets. Because each wavelength bends differently, hitting all three at once requires understanding the spread — the angular difference between red and violet through the same prism at the same angle.

SYNTHESIS mode introduces a second optical element: a flat mirror. The mirror reflects all wavelengths identically, with no colour separation, redirecting the entire rainbow as a unit. Two targets at different positions require specific wavelengths to arrive via different paths. The player must position and angle both the prism and the mirror — different adjustments serving different wavelengths — to route red to one target and violet to another simultaneously.

Total internal reflection is modelled correctly. If the player tilts a prism past the critical angle — arcsin of one over the refractive index — a beam that should exit instead bounces back inside the glass and emerges from a different face entirely. The effect appears suddenly, without warning, exactly as it does in a real laboratory. The player discovers critical angle by accidentally triggering it.

The daily alignment challenge presents one shared optical arrangement to all players. The global leaderboard ranks by elegance — the number of elements used — rewarding the player who solves with two elements what most players solve with four.