Exploring the Science of Light
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Mix and Match

Mix and match colors with light

Required Materials

  • 1 piece of white paper

  • 4 clear plastic cups

  • Red, yellow, green and blue food coloring

  • Pencil

  • Flashlight

  • Newspaper

  • 4 cotton swabs

  • Water

  • Ruler

Activity Directions

  1. Cover your workspace with newspaper.
  2. Place a few drops of red food coloring on one end of a cotton swab.
  3. Using the swab, make a dark red dot about 2 cm in diameter on the white paper. Repeat this process with each of the remaining 3 colors.
  4. Fill each cup halfway with water.
  5. Add 3–5 drops of food coloring to each cup (a different color in each cup), and mix with a matching swab.
  6. Turn on the flashlight and darken the room.
  7. Hold the cup of red water directly above the red dot.
  8. Shine the flashlight straight down into the cup of red water and look at the red dot. What color do you see? Record your results in the chart.
  9. Repeat the process until you have tried all the water colors with all the colored dots. The data chart will help you keep track of the combinations you tested.
    • Water Color Dot Color Color You See
      Red Red
      Red Blue
      Red Yellow
      Red Green
      Blue Red
      Blue Blue
      Blue Yellow
      Blue Green
      Yellow Red
      Yellow Blue
      Yellow Yellow
      Yellow Green
      Green Red
      Green Blue
      Green Yellow
      Green Green
  10. What did you discover about mixing color and light? Does it make a difference if you set the cup down or hold it above the dot? Do you get the same result for blue if you make really dark blue water?
  11. You’ve just mixed different wavelengths together. When you are looking into the red water as it is held above a yellow dot, you see two wavelengths at the same time. The wavelength for red and yellow combine and you see orange.
  12. Visible light contains ROY G BIV, with three of the seven colors considered primary: red, yellow, and blue. Primary colors can be combined to make the other colors of the rainbow. Red + yellow = orange. Look at where orange is in ROY. Now what colors make green? Is the order of colors in a rainbow a coincidence?

Want to mix colors online? Visit these cool websites:

Project Lite: Addition Photo
Project Lite: Einstein

Want to Learn More? Read an article related to this activity:

To find this experiment and many more please download the Lighten Up! Discovering the Science of Light book, developed through a partnership with the Optical Society of America’s Foundation (OSAF) and the Girl Scouts of the USA.

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