Make a spectroscope
Build a simple cardboard-and-CD spectroscope to split light into colors, observe spectra from different light sources, and learn about how light wavelengths vary.
About this activity
Build a simple cardboard-and-CD spectroscope to split light into colors, observe spectra from different light sources, and learn about how light wavelengths vary.
What you need
Step by step
- 1
Step 1
Gather all the materials on a clean table so everything is ready.
- 2
Step 2
Cut a small rectangular viewing window about 1.5 cm wide and 1 cm tall near one end of the tube using scissors.
- 3
Step 3
Line the inside of the tube with black construction paper and tape it flat to make the interior dark.
- 4
Step 4
Measure and mark the opposite end of the tube about 10 cm from the viewing window to place the light slit.
- 5
Step 5
Cut a narrow straight slit about 1 mm wide and 1 cm tall at the marked end using the craft knife with adult supervision.
- 6
Step 6
Cut a small triangular piece from the CD about 3 cm wide using strong scissors with adult supervision.
- 7
Step 7
Tape the CD piece inside the tube at a 45 degree angle near the viewing window with the shiny side facing the slit.
- 8
Step 8
Seal gaps around the CD piece with tape so light only enters through the slit.
- 9
Step 9
Hold the spectroscope so the slit faces a light source and keep the viewing window at your eye level.
- 10
Step 10
Look through the viewing window to see the colored bands and note what you see.
- 11
Step 11
Repeat Steps 9 and 10 for different light sources and draw each spectrum on paper labeling the light source.
- 12
Step 12
Share your finished spectroscope and your drawings on DIY.org
Fun facts
How do you make a cardboard-and-CD spectroscope?
To build a simple spectroscope, cut a narrow slit (about 1–2 mm) in a strip of cardboard or two pieces taped slightly apart—adult help required for sharp tools. Roll a cardboard tube or fold a small cereal box into a viewing tube and secure it. Angle a CD/DVD inside so the shiny side reflects the light from the slit toward an eyepiece hole. Paint or line the inside with black paper to reduce stray light. Look through the eyepiece at different light sources to see separated colors.
What materials do I need for a cardboard-and-CD spectroscope?
You’ll need a discarded CD or DVD, sturdy cardboard (tube, cereal box, or thick card), scissors or craft knife (adult use), tape or glue, ruler, pencil, and black paper or paint to darken the interior. Optional: diffraction grating film for clearer spectra, aluminum foil to block stray light, and a small clamp or rubber bands to hold components steady. Use a lamp, LED, or daylight for observing different spectra.
What ages is this spectroscope activity suitable for?
This hands-on project suits ages about 7–13 with adult supervision for cutting and handling sharp tools. Younger children (4–6) can enjoy observing spectra and sorting colors while adults or older kids do the construction. Teens can extend the activity by measuring line positions, comparing light sources, or photographing spectra. Always supervise eye-level experiments and tool use; adapt steps to skill level.
What safety tips, learning benefits, and variations should we consider?
Safety: never point the spectroscope at the sun and supervise cutting tools and sharp CD edges. Benefits: it teaches light behavior, wavelength concepts, observation and recording skills, and the scientific method. Variations: replace a CD with diffraction grating film for clearer lines, use a smartphone camera to capture spectra, compare LEDs, incandescent bulbs, and sunlight, or add labeled charts to identify emission and absorption features.
Watch & Learn
Need help?
What can I use instead of a CD if I can't find one?
If you don't have a CD for Step 6, use a DVD, a small piece of reflective gift-wrap, or a handheld plastic diffraction grating and tape it inside at a 45° angle with the shiny side facing the slit.
I don't see any colors — what might be wrong?
If you see no or washed-out colors, make sure the slit you cut in Step 5 is narrow and straight (about 1 mm wide), the tube interior is fully lined with black construction paper per Step 3, and the CD piece in Step 7 is positioned at 45° with gaps sealed in Step 8.
How can I adapt the steps for younger or older children?
For preschoolers, have an adult complete the Step 2 viewing-window cut, the Step 5 slit, and the Step 6 CD cutting while the child tapes the CD in Step 7 and draws spectra in Step 11, while older kids can measure the 10 cm mark in Step 4, cut the slit themselves with supervision, and compare multiple light sources in Steps 9–11.
How can we extend or personalize the spectroscope project?
To extend the activity, try swapping different slit widths in Step 5 or interchangeable CD/diffraction pieces from Step 6, mount the tube for steadier viewing in Step 9, photograph the spectra you see in Step 10, and make labeled comparison charts from your drawings in Step 11 to share on DIY.org.