Six little instruments, one octave of spectrum. Each one starts with a question: make your guess, then run the experiment yourself. The strip below stays lit the whole time, showing which wavelengths each experiment is touching. Six manipulations of the same thing.
The visible octave · 750 nm to 380 nm
Everything here runs on the real physics in miniature: dispersion in glass, interference from a CD's 1.6 µm track spacing, the 42° water-droplet cone, Rayleigh's 1/λ⁴ scattering, two reflections a few hundred nanometres apart in a soap film, and a hologram's fringes solved from |O + R|² and read back out with the grating equation. Illustrative in scale, honest in mechanism. Want a full optical bench with lenses, mirrors, and dispersive glass you arrange yourself? The open-source Ray Optics Simulation is the deep end of this pool.