demonstrations:make_rainbow_with_a_cd

Make Rainbow With a CD

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required

Categories: Electromagnetic Spectrum and Waves, Light

Alternative titles: Creating Light Patterns with a CD

Summary

This colorful experiment explores how light interacts with the reflective surface of a CD to create rainbow patterns.

Procedure

  1. Gather materials: a blank or old CD, paper, scissors, tape, and a pencil.
  2. Find a sunny location where the CD can reflect sunlight onto a blank wall or white poster board.
  3. Hold the shiny side of the CD toward the sunlight and observe the rainbow reflection on the wall. Note the colors and shapes.
  4. Trace the CD onto sheets of paper several times and cut out circular pieces.
  5. Fold and cut these circles into snowflake or geometric designs.

How to make a rainbow colors with a CD - Kids Fun Science:


📄 Rainbow Science: Creating Light Patterns with a CD - Buggy and Buddy: https://buggyandbuddy.com/rainbow-science-create-light-patterns-with-a-cd/

Variations

  • Use a flashlight instead of sunlight for indoor exploration.
  • Try using colored or translucent paper snowflakes to see how color affects the light patterns.
  • Experiment with DVDs or Blu-ray discs and compare the sharpness and color of the reflections.
  • Use black paper cutouts to create shadow-based rainbow designs.

Safety Precautions

  • Never look directly at the sun while using the CD, only observe the reflection on a surface.
  • Supervise young children when using scissors to cut paper.
  • Avoid using sharp or cracked CDs that could cause injury.

Questions to Consider

  • Why does a CD produce rainbow colors when light hits it? (The CD’s surface has tiny, evenly spaced grooves that act as a diffraction grating, separating white light into its component colors.)
  • What happens when you change the angle of the CD? (The reflected light shifts, altering the shape and position of the rainbow.)
  • How does adding paper snowflakes change the light pattern? (The paper blocks some light rays, creating new shadow and diffraction patterns.)
  • How is this similar to how a prism creates a rainbow? (Both separate white light into its spectrum through diffraction or refraction.)