Making a spectroscope: why meteors have colours
The question
Can a homemade spectroscope separate the colours from different lamps, and what do the colours of meteors tell us?
Meteor colours come from glowing atoms of the meteoroid and the air: sodium gives orange-yellow, magnesium and iron blue-green or yellow, and nitrogen and oxygen in the air add red and green. Spectra let scientists measure what meteoroids are made of.
Equipment
- A cardboard tube or box, black tape and a narrow slit made from two razor-straight card edges
- A diffraction grating slide (about 500 lines per mm) or a piece of old CD
- Light sources: a filament bulb, an LED torch, a fluorescent lamp, and an orange sodium street lamp viewed from a distance at night
- A phone camera
Method
- Build the spectroscope with the slit at one end and the grating at the other.
- Point it at each light source and photograph the spectrum through the grating.
- Compare continuous spectra (filament bulb) with line spectra (fluorescent and street lamps).
- Use the site's pages to match the lines to the colours seen in meteors.
- What to measure
- Photographs of each spectrum and the positions of the bright lines compared with a filament bulb's continuous spectrum.
- How to present it
- A gallery of spectra, an explanation of line spectra, and a chart linking meteor colours to the elements that produce them.
- Take it further
- Find out how professional meteor cameras with gratings record the spectra of real meteors.
Safety
Never point the spectroscope at the Sun. Keep blades for cutting with an adult, and do not use mains equipment with exposed wiring.