ScienceVerseHomemade CD Spectroscope
Sign in to save this experiment.Safety first
Adult supervision requiredAn adult must be present and should do the cutting with scissors. Never point the spectroscope at the Sun and never look at the Sun, with or without it: looking at the bright Sun can cause severe eye injury. Use indoor lamps only. Do not cut or break the CD, because broken discs have sharp edges.
Protective equipment and “do not substitute” warnings have not been recorded for this experiment yet. They are added when its safety review is completed; until then, follow the supervision notes above.
Disposal: Recycle the cardboard. Keep the CD for reuse, or take it to a recycling point that accepts discs.
Do not start this experiment until an adult who has read the supervision notes above is present.
An adult needs to be here first
The materials (6) and steps (6) for this experiment are hidden until an adult who has read the safety information above is present.
What you should see
- A band of rainbow colours appears on the CD.
- A filament bulb gives a smooth rainbow in which each colour shades into the next.
- A fluorescent tube or compact fluorescent bulb shows separate bright coloured lines on top of the colours.
Why it works
The tracks on a CD are very closely spaced and act as a diffraction grating. Light reflected from them spreads out, and different colours (different wavelengths) spread out at different angles, so white light is separated into a spectrum.
A filament bulb glows because its filament is hot, and it gives a continuous spectrum. In a fluorescent lamp, electricity excites mercury vapour, which gives out only certain colours, seen as distinct lines; the lamp's coating adds some continuous colour as well.
Learn the ideas behind it
Explore it further
The same ideas, as something you can change and watch on screen:
Sources
- College Physics 2e, 27.4 Multiple Slit Diffraction — OpenStax
- Cereal box spectroscope (SOHO classroom activity) — NASA / ESA SOHO
- Eclipse Safety — NASA Science