Level 8: Spectra

Waves, sound and light · level 8 of 8 · rough age 17 and beyond (a guide for parents; anyone can start anywhere)

The last level reads the fingerprints that atoms leave in light. You meet photons and energy levels, work out the hydrogen lines from the Rydberg formula, and see how cool gas cuts dark lines into a spectrum. A diffraction grating spreads the lines apart; a rover's laser makes rocks glow so their elements can be read from metres away; and the Doppler shift of a line measures how fast things move.

Lesson	You will be able to
Photons and energy levels	Use \(E = hf = hc/\lambda\) and energy levels in eV
Emission lines	Find hydrogen's visible lines with the Rydberg formula
Absorption lines	Explain dark lines in sunlight and in light through a planet's air
The diffraction grating	Use \(d\sin\theta = n\lambda\) and find the resolving power needed
Reading rocks with lasers	Explain how SuperCam finds the elements and minerals in a rock
Doppler shifts of light	Use \(\Delta\lambda/\lambda = v/c\) to measure speeds from spectra

Previous: Level 7: Lenses and telescopes · Waves, sound and light topic page · The companion level: Heat and matter, level 8