The Spectroscope

A bench that disperses light into a spectrum — through a glass prism (Cauchy n(λ), Snell at both faces, near minimum deviation) or a diffraction grating (d·sinθ_m=mλ) — then reads the real line spectrum of a chosen source, each line at its true visible colour.

Disperser

Apex angle 60°

Source

Look

Switch the disperser to compare refractive vs. diffractive spreading; switch the source to read its fingerprint. Balmer lines are computed live from the Rydberg formula; colours come from a CIE wavelength→sRGB map. The self-test proves the physics.

Feat of Light: a reading mark sits on the band at Hα — choose a source whose line falls under it to read the spectrum.

← the cross

← The Rydberg Constant Read a constant off your own lines: hand the four Balmer wavelengths to a blind line-fitter; slope −R, intercept R/4. It knows no atomic physics.